MDCAT Current Electricity MCQs

This comprehensive set of MCQs on Current Electricity is designed to cover all essential topics required for success in the Medical and Dental College Admission Test (MDCAT). Focused on key subjects such as Ohm’s Law, Resistance, Resistivity, Electric Circuits, and Power, these MCQs are crafted to help aspiring medical and dental students build a strong understanding of electric current and its applications in health sciences.

Who should practice Current Electricity MCQs?

Students preparing for the MDCAT who wish to deepen their understanding of electric current, circuits, and their roles in various medical technologies and devices.
Individuals seeking to enhance their knowledge of electric potential difference, resistance, and the functioning of electrical components essential for healthcare and diagnostic equipment.
University students targeting high-yield topics like the effects of electric current in biological systems and the use of electricity in medical treatments.
Anyone aiming to strengthen their foundational understanding of current electricity and its implications in fields like electrotherapy and medical diagnostics.
Candidates focused on developing critical thinking and analytical skills related to solving electric circuit problems and applying electrical principles to real-world medical scenarios.

1. According to Ohm’s law, the current flowing through a conductor is directly proportional to the:

A) Voltage across the conductor
B) Resistance of the conductor
C) Power in the circuit
D) Length of the conductor

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2. The SI unit of electrical resistance is:

A) Volt
B) Ohm
C) Ampere
D) Coulomb

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3. What is the specific resistance (resistivity) of a material?

A) Resistance per unit length
B) Resistance per unit area
C) Resistance per unit volume
D) Resistance per unit length and cross-sectional area

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4. Which of the following increases the resistance of a wire?

A) Increasing the temperature
B) Decreasing the length of the wire
C) Increasing the cross-sectional area
D) Decreasing the temperature

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5. The temperature coefficient of resistance is defined as:

A) The ratio of resistivity to temperature
B) The change in resistance per unit length
C) The change in resistance per unit rise in temperature
D) The change in resistivity per unit rise in temperature

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6. How does the resistivity of metals change with an increase in temperature?

A) Increases
B) Decreases
C) Remains constant
D) Becomes zero

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7. What is the internal resistance of a power supply?

A) Resistance of the circuit
B) Resistance within the power source itself
C) Resistance of the connecting wires
D) Resistance due to temperature change

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8. The formula to calculate electric power is:

A) P = IV
B) P = V/R
C) P = IR
D) P = I^2R

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9. The SI unit of electric power is:

A) Watt
B) Joule
C) Kilowatt-hour
D) Volt

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10. What is the relation between power and energy?

A) Power is energy per unit time
B) Power is energy times voltage
C) Power is energy times current
D) Power and energy are unrelated

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11. What is the value of 1 kilowatt-hour in joules?

A) 3.6 x 10^3 J
B) 3.6 x 10^5 J
C) 3.6 x 10^6 J
D) 3.6 x 10^7 J

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12. What happens to the resistance of a conductor if the length is doubled?

A) The resistance is halved
B) The resistance remains the same
C) The resistance doubles
D) The resistance becomes zero

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13. Which material has the lowest resistivity at room temperature?

A) Silver
B) Copper
C) Iron
D) Aluminum

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14. A higher temperature coefficient of resistance means that the material’s resistance:

A) Increases more with temperature
B) Decreases more with temperature
C) Remains constant with temperature
D) Decreases to zero

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15. What is the formula for resistance in terms of resistivity, length, and cross-sectional area?

A) R = ρL/A
B) R = ρA/L
C) R = ρL²/A
D) R = A/ρL

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16. How is the internal resistance of a power source related to the voltage drop?

A) Increases the voltage drop
B) Decreases the voltage drop
C) Has no effect on the voltage drop
D) Completely removes the voltage drop

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17. What is the unit of the temperature coefficient of resistance?

A) °C
B) Ohm/°C
C) 1/°C
D) Ohm-m

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18. How does resistivity vary with temperature for a semiconductor?

A) Increases with temperature
B) Decreases with temperature
C) Remains constant
D) Becomes infinite

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19. What happens to the resistance of a wire if its cross-sectional area is doubled?

A) Resistance is halved
B) Resistance is doubled
C) Resistance remains the same
D) Resistance becomes zero

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20. The total resistance of resistors connected in parallel is:

A) Greater than the largest resistor
B) Less than the smallest resistor
C) Equal to the sum of all resistances
D) Equal to the average of all resistances

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21. If the voltage across a resistor is doubled while the resistance remains the same, what happens to the current?

A) It is halved
B) It doubles
C) It remains the same
D) It becomes zero

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22. What happens to the resistance of a metal conductor when the temperature decreases?

A) Increases
B) Decreases
C) Remains constant
D) Becomes infinite

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23. Which quantity does not change in a series circuit?

A) Voltage
B) Current
C) Resistance
D) Power

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24. The resistivity of a material depends on:

A) Length of the material
B) Cross-sectional area
C) Temperature
D) Voltage

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25. How is the electric power related to the resistance in a circuit?

A) P = I^2R
B) P = V^2/R
C) P = IV
D) Both A and B

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26. The internal resistance of a cell is negligible when:

A) The cell is ideal
B) The current is small
C) The current is large
D) The voltage is large

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27. How does the resistance of a conductor vary with length?

A) Directly proportional
B) Inversely proportional
C) Exponentially proportional
D) No relation

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28. The unit of specific resistance (resistivity) is:

A) Ohm
B) Ohm-meter
C) Volt/ampere
D) Coulomb/meter

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29. The amount of energy used by a 100W device running for 10 hours is:

A) 1 kWh
B) 10 kWh
C) 100 kWh
D) 1000 kWh

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30. What is the temperature coefficient of resistance for conductors?

A) Positive
B) Negative
C) Zero
D) Infinite

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31. If two resistors are connected in series, their equivalent resistance is:

A) The sum of their resistances
B) The product of their resistances
C) The average of their resistances
D) Zero

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32. A resistor of 2 ohms carries a current of 3A. What is the power dissipated?

A) 6 W
B) 9 W
C) 18 W
D) 12 W

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33. What happens to the resistance of a wire if its length and cross-sectional area are both doubled?

A) Resistance remains unchanged
B) Resistance is halved
C) Resistance is doubled
D) Resistance is quadrupled

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34. The energy stored in a capacitor is given by which formula?

A) U = 1/2 CV^2
B) U = CV^2
C) U = QV
D) U = 1/2 QV

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35. Which factor primarily affects the internal resistance of a battery?

A) Temperature
B) Terminal voltage
C) External resistance
D) Current

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36. What is the relationship between voltage (V), current (I), and resistance (R) according to Ohm’s Law?

A) V = IR
B) V = I/R
C) V = R/I
D) V = I^2R

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37. Which of the following defines 1 watt of power?

A) 1 joule per second
B) 1 volt per ampere
C) 1 ohm per meter
D) 1 coulomb per second

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38. Which unit is used to measure electrical energy in domestic use?

A) Watt
B) Kilowatt-hour
C) Joule
D) Volt

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39. If the resistivity of a material increases with temperature, the material is:

A) A conductor
B) A semiconductor
C) An insulator
D) A superconductor

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40. What happens to the total resistance in a parallel circuit when more resistors are added?

A) Increases
B) Decreases
C) Remains the same
D) Becomes infinite

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41. The internal resistance of a battery causes the terminal voltage to:

A) Increase
B) Decrease
C) Remain constant
D) Become zero

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42. The resistance of a wire depends on which of the following factors?

A) Length and area
B) Material and temperature
C) Both A and B
D) Neither A nor B

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43. A power of 1 kW is equal to:

A) 1000 joules
B) 1000 watts
C) 1000 newtons
D) 1000 volts

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44. What happens to the potential difference across a resistor when the current through it increases?

A) It increases
B) It decreases
C) It remains the same
D) It becomes zero

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45. Resistivity is independent of:

A) Length
B) Cross-sectional area
C) Temperature
D) Material

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46. Which of the following is true for a superconductor?

A) It has zero resistance
B) It has infinite resistance
C) It has constant resistance
D) It behaves as an insulator

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47. The total energy consumed by a 50W device in 5 hours is:

A) 0.25 kWh
B) 0.50 kWh
C) 1.25 kWh
D) 2.50 kWh

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48. In a circuit, if the voltage remains constant and the resistance is halved, the current:

A) Doubles
B) Halves
C) Remains constant
D) Becomes zero

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49. Electric power is the product of:

A) Voltage and current
B) Voltage and resistance
C) Current and resistance
D) Resistance and energy

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50. What is the equivalent resistance of two resistors of 6 ohms each connected in parallel?

A) 3 ohms
B) 12 ohms
C) 1 ohm
D) 2 ohms

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51. What happens to the power dissipated in a resistor if the current is tripled?

A) Power triples
B) Power becomes 9 times
C) Power halves
D) Power remains the same

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52. The resistivity of a semiconductor:

A) Decreases with increasing temperature
B) Increases with increasing temperature
C) Remains constant
D) Becomes zero at high temperature

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53. The unit of electrical energy is:

A) Joule
B) Watt
C) Coulomb
D) Volt

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54. What is the SI unit of the temperature coefficient of resistance?

A) Ohm
B) Ohm/meter
C) Per degree Celsius
D) Joules

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55. If a conductor’s length is doubled while keeping its cross-sectional area the same, what happens to its resistance?

A) It doubles
B) It halves
C) It remains constant
D) It quadruples

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56. The internal resistance of a power supply causes a drop in:

A) Current
B) Voltage
C) Resistance
D) Power

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57. A device used to measure resistance is called:

A) Voltmeter
B) Ammeter
C) Ohmmeter
D) Galvanometer

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58. The electric power consumed by a device is given by which formula?

A) P = IV
B) P = I^2R
C) P = V^2/R
D) All of the above

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59. What is the resistance of a wire if its resistivity is 1.7 × 10^(-8) Ωm, length is 5 m, and cross-sectional area is 1 × 10^(-6) m^2?

A) 0.085 Ω
B) 0.0085 Ω
C) 0.17 Ω
D) 8.5 Ω

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60. What happens to the internal resistance of a battery as it ages?

A) Increases
B) Decreases
C) Remains the same
D) Becomes zero

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61. If two resistors are connected in parallel, the total resistance is:

A) Less than the smallest resistor
B) Equal to the sum of the resistors
C) Greater than the largest resistor
D) The average of the two resistors

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62. What is the unit of electrical power?

A) Joules
B) Watts
C) Coulombs
D) Volts

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63. If the resistance of a wire is 10 ohms at 20°C, and its temperature coefficient is 0.003/°C, what is its resistance at 40°C?

A) 10.6 ohms
B) 12.0 ohms
C) 10.3 ohms
D) 9.7 ohms

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64. What happens to the resistivity of a material when the temperature increases?

A) Increases for conductors
B) Decreases for semiconductors
C) Remains constant for insulators
D) Both A and B

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65. The power dissipated in a circuit with a resistance of 5 ohms and a current of 2A is:

A) 10 W
B) 20 W
C) 40 W
D) 8 W

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66. Which device is used to store electrical energy?

A) Resistor
B) Capacitor
C) Inductor
D) Diode

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67. Which of the following statements is true for Ohm’s law?

A) V = IR is always valid for all materials
B) V = IR is valid only for ohmic conductors
C) Ohm’s law holds at high temperatures
D) Ohm’s law is invalid for metallic conductors

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68. The internal resistance of a power supply is responsible for:

A) Energy loss inside the supply
B) Increase in external voltage
C) Decrease in current
D) Power gain

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69. The energy consumed by a 60W light bulb in 2 hours is:

A) 0.12 kWh
B) 0.5 kWh
C) 0.15 kWh
D) 1.2 kWh

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70. The unit of electrical resistivity is:

A) Ohm
B) Ohm-meter
C) Volt
D) Joule

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71. If two resistors of 4Ω and 6Ω are connected in series, their equivalent resistance is:

A) 10 Ω
B) 2.4 Ω
C) 24 Ω
D) 1.5 Ω

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72. In a parallel circuit, what happens to the current through each resistor if the total current increases?

A) Decreases
B) Increases
C) Remains the same
D) Becomes zero

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73. A current of 2A flows through a resistor of 8 ohms. What is the voltage across the resistor?

A) 16V
B) 8V
C) 4V
D) 32V

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74. A material with a high resistivity is a:

A) Good conductor
B) Poor conductor
C) Insulator
D) Semiconductor

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75. The internal resistance of a cell:

A) Decreases its terminal voltage
B) Increases its terminal voltage
C) Does not affect the voltage
D) Becomes zero in a closed circuit

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76. In a series circuit, the current is:

A) The same through all components
B) Different for each component
C) Zero through each resistor
D) Proportional to the resistance

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77. What is the total power consumed by three resistors connected in series if each resistor dissipates 10W?

A) 30W
B) 10W
C) 100W
D) 300W

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78. A kilowatt-hour is a unit of:

A) Power
B) Energy
C) Charge
D) Voltage

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79. The temperature coefficient of resistance for a material is the rate of:

A) Change in resistance with temperature
B) Increase in voltage with resistance
C) Decrease in current with resistance
D) Variation of energy with resistance

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80. Which of the following is a good conductor of electricity?

A) Copper
B) Glass
C) Plastic
D) Rubber

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81. In an electric circuit, the potential difference is measured using:

A) Ammeter
B) Voltmeter
C) Galvanometer
D) Ohmmeter

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82. What happens to the total current in a circuit when resistors are connected in parallel?

A) It decreases
B) It increases
C) It remains the same
D) It becomes zero

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83. What is the SI unit of electrical resistance?

A) Volt
B) Ampere
C) Ohm
D) Watt

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84. The internal resistance of an ideal voltage source is:

A) Zero
B) Infinity
C) Very high
D) Very low

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85. If the current in a circuit is halved, the power dissipated will be:

A) Halved
B) Quartered
C) Doubled
D) Remains the same

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86. Which factor increases the resistivity of a metal?

A) Increasing temperature
B) Decreasing temperature
C) Decreasing length
D) Increasing cross-sectional area

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87. How is the total resistance calculated for resistors in parallel?

A) Inversely proportional to the sum of reciprocals of resistances
B) Directly proportional to the sum of resistances
C) Product of resistances divided by sum
D) Sum of squares of resistances

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88. In which form is energy usually lost in a resistor?

A) Mechanical
B) Heat
C) Chemical
D) Magnetic

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89. The resistivity of a conductor depends on:

A) Length and cross-sectional area
B) Temperature
C) Material of the conductor
D) Both B and C

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90. The power rating of an electrical appliance is usually given in:

A) Volts
B) Joules
C) Watts
D) Ohms

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91. What is the relationship between power, voltage, and current in a circuit?

A) P = V × I
B) P = V/I
C) P = I²/R
D) P = V²/R

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92. A device that converts electrical energy into mechanical energy is called:

A) Resistor
B) Motor
C) Transformer
D) Generator

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93. What is the resistance of a 100W, 220V light bulb?

A) 220 ohms
B) 484 ohms
C) 100 ohms
D) 10 ohms

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94. In a series circuit, how is the total resistance calculated?

A) The sum of all resistances
B) The product of all resistances
C) The reciprocal of all resistances
D) The difference of all resistances

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95. The resistance of a wire is inversely proportional to:

A) Its length
B) Its temperature
C) Its cross-sectional area
D) Its resistivity

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96. If the current in a conductor doubles, the heat produced will:

A) Double
B) Remain the same
C) Quadruple
D) Halve

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97. The kilowatt-hour is commonly used to measure:

A) Electric current
B) Electric power
C) Electrical energy
D) Electric charge

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98. A material with zero electrical resistance at very low temperatures is known as a:

A) Conductor
B) Insulator
C) Semiconductor
D) Superconductor

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99. What is the temperature coefficient of resistance for metals?

A) Positive
B) Negative
C) Zero
D) Depends on the material

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100. What is the power dissipated by a resistor of resistance 5Ω with a current of 3A flowing through it?

A) 15W
B) 45W
C) 9W
D) 25W

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