Current Electricity

Current Electricity MDCAT MCQs with answers

112 past paper MCQs from Physics unit 9, Current Electricity, across 5 topics. They are arranged topic by topic; bigger topics show a sample here and link to their full set and to study notes. Tap “Show answer” for the correct option and a short solution.

Practise as a quiz

Steady Current

1.A charge of 90 C passes through a wire for 30 seconds. The current in the wire will be: (MDCAT 2024)

  1. 3 A
  2. 0.3 A
  3. 3 mA
  4. 0.3 mA
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Correct answer: (a) 3 A

$I=q/t=90/30=3$ A.

2.152.A charge of 90 C passes through a wire for 30 seconds. Then the current in the wire will be: (UHS MDCAT 2024)

  1. 3A
  2. 0.3 A
  3. 3 mA
  4. 0.3 mA
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Correct answer: (a) 3A

$I=q/t=90/30$, which is $3\,\mathrm{A}$.

3.What does one Coulomb represent in terms of charge? (KMU MDCAT 2024)

  1. The amount of charge transported by a current of one Ampere in one second
  2. The charge of one proton
  3. The charge of one electron
  4. The charge required to create a force of 1 Newton between two charges separated by 1meter
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Correct answer: (a) The amount of charge transported by a current of one Ampere in one second

One coulomb is the charge carried past a point by one ampere in one second.

All 14 Steady Current MCQs → Steady Current notes →

Ohm’s Law

4.The statement that the magnitude of the current in a metal is proportional to the potential difference across it as long as the temperature of the conductor is kept constant is known as: (MDCAT 2024)

  1. Joule's law
  2. Gauss's law
  3. Ohm's law
  4. Ampere's law
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Correct answer: (c) Ohm's law

That proportionality at constant temperature is Ohm's law, $V=IR$.

5.A resistor of \$6\,\Omega\$ with a tolerance of 10% and another of \$4\,\Omega\$ with a tolerance of 10% are joined in series. The tolerance of the combination is about: (UHS MDCAT 2017)

  1. 5%
  2. 12%
  3. 10%
  4. 13%
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Correct answer: (c) 10%

The uncertainties add: $0.6+0.4=1.0\,\Omega$ in $10\,\Omega$, which is again 10%.

6.A wire of resistance \$4\,\Omega\$ is bent into a circle. The resistance between the ends of any diameter is: (UHS MDCAT 2017)

  1. $1\,\Omega$
  2. $2\,\Omega$
  3. $4\,\Omega$
  4. $8\,\Omega$
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Correct answer: (a) $1\,\Omega$

A diameter splits the wire into two $2\,\Omega$ halves in parallel, giving $1\,\Omega$.

All 47 Ohm’s Law MCQs → Ohm’s Law notes →

Resistivity and its Temperature Dependence

7.The unit of resistivity is the: (MDCAT 2020)

  1. ohm
  2. ohm metre
  3. ohm per metre
  4. metre per ohm
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Correct answer: (b) ohm metre

From $\rho=RA/L$ the unit is the ohm metre.

8.The resistance of a conductor does not depend on which of the following? (MDCAT 2022)

  1. area of cross-section
  2. resistivity
  3. length
  4. mass
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Correct answer: (d) mass

$R=\rho L/A$ has no mass in it.

9.What do substances whose resistance decreases with a rise in temperature have? (MDCAT 2022)

  1. a high temperature coefficient
  2. a negative temperature coefficient
  3. a positive temperature coefficient
  4. a zero temperature coefficient
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Correct answer: (b) a negative temperature coefficient

A falling resistance means the temperature coefficient of resistance is negative, as it is for semiconductors.

All 35 Resistivity and its Temperature Dependence MCQs → Resistivity and its Temperature Dependence notes →

Internal Resistance of a Source

10.The terminal voltage $V_t$ of a battery is greater than the emf of the battery when the: (MDCAT 2020)

  1. battery is charging
  2. battery is discharging
  3. battery is connected with a resistance
  4. battery is connected with a voltmeter
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Correct answer: (a) battery is charging

While charging, the current is driven into the battery, so $V_t=\varepsilon+Ir$ is above the emf.

11.A low voltage supply of e.m.f. 20 V and internal resistance $1.5\ \Omega$ is used to work a heater of resistance $6.5\ \Omega$ in a fish tank. What is the power delivered to the water in the fish tank? (MDCAT 2022)

  1. 41 W
  2. 50 W
  3. 53 W
  4. 62 W
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Correct answer: (a) 41 W

$I=20/(1.5+6.5)=2.5$ A, so $P=I^2R=(2.5)^2(6.5)\approx41$ W.

12.When current is neither drawn from a source nor given to it, then: (UHS MDCAT 2017)

  1. $E=V_T$
  2. $V_T>E$
  3. $E>V_T$
  4. both $V_T>E$ and $E>V_T$
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Correct answer: (a) $E=V_T$

With no current there is no drop across the internal resistance, so the terminal potential difference equals the emf.

All 12 Internal Resistance of a Source MCQs → Internal Resistance of a Source notes →

Maximum Power Transfer

13.Volt $\times$ ampere is the measure of: (MDCAT 2024)

  1. current
  2. potential difference
  3. resistance
  4. power
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Correct answer: (d) power

$P=VI$, so a volt-ampere is a watt.

14.The maximum power transfer theorem states that maximum power is delivered to the load when (KMU MDCAT 2024)

  1. The load resistance is half of the source resistance
  2. The load resistance is zero
  3. The load resistance is double the source resistance
  4. The load resistance is equal to the source resistance
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Correct answer: (d) The load resistance is equal to the source resistance

Most power reaches the load when its resistance matches the internal resistance of the source.

15.Which equation represents the maximum output power of source? (PMC MDCAT 2022)

  1. P = VI
  2. P = I2R
  3. P = V2/R
  4. P = E2/4R
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Correct answer: (d) P = E2/4R

Most power reaches the load when its resistance matches the internal one, and then $P=E^2/4R$.

16.Maximum power delivered by a battery is? (PMC Practice 2021)

  1. Pmax = E2/4r
  2. Pmax =4rE2
  3. Pmax =VIT
  4. Unlimited
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Correct answer: (a) Pmax = E2/4r

Most power is delivered when the load matches the internal resistance, and then $P=E^2/4r$.

Maximum Power Transfer notes →

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