Grade 12 : Physics - Current Electricity (Set 1)

Question 1

A total electric charge of 120 C passes through a cross-section of a wire in 60 seconds. What is the magnitude of the electric current flowing through the wire?

Accepted Answer

C) 2.0 A

Answer

A) 0.5 A

Answer

B) 1.0 A

Answer

D) 4.0 A

Question 2

An electric conductor has a resistance of $15\ \Omega$ and carries a current of 3.0 A. What is the potential difference across the ends of the conductor?

Accepted Answer

D) 45.0 V

Answer

A) 5.0 V

Answer

B) 12.0 V

Answer

C) 30.0 V

Question 3

A cylindrical conductor of length $L$ and cross-sectional area $A$ has resistance $R$. If its length is stretched to $2L$ while maintaining a constant cross-sectional area $A$, how does its resistance change?

Accepted Answer

C) Resistance is doubled

Answer

A) Resistance is halved

Answer

B) Resistance remains unchanged

Answer

D) Resistance is quadrupled

Question 4

Three resistors of resistance $4.0\ \Omega$, $6.0\ \Omega$, and $10.0\ \Omega$ are connected in series. What is the equivalent resistance of the combination?

Accepted Answer

C) 20.0 \Omega

Answer

A) 1.9 \Omega

Answer

B) 10.0 \Omega

Answer

D) 240.0 \Omega

Question 5

Two resistors of $6.0\ \Omega$ and $12.0\ \Omega$ are connected in parallel across a circuit. Calculate the equivalent resistance of this parallel combination.

Accepted Answer

A) 4.0 \Omega

Answer

B) 6.0 \Omega

Answer

C) 9.0 \Omega

Answer

D) 18.0 \Omega

Question 6

An electrical appliance operates at a potential difference of 220 V and draws a current of 2.0 A. What is the electric power consumed by the appliance?

Accepted Answer

C) 440 W

Answer

A) 110 W

Answer

B) 220 W

Answer

D) 880 W

Question 7

A 100 W light bulb is kept switched on continuously for 5 hours. How much electrical energy does it consume in kilowatt-hours (kWh)?

Accepted Answer

B) 0.5 kWh

Answer

A) 0.05 kWh

Answer

C) 5.0 kWh

Answer

D) 500 kWh

Question 8

The drift velocity of free electrons in a metallic wire carrying current $I$ is $v_d$. If the current in the same wire is increased to $2I$, what is the new drift velocity?

Accepted Answer

C) 2 v_d

Answer

A) v_d / 2

Answer

B) v_d

Answer

D) 4 v_d

Question 9

For a metallic conductor, how does its electrical resistance change when its temperature increases?

Accepted Answer

B) Increases

Answer

A) Decreases linearly

Answer

C) Remains unchanged

Answer

D) Drops abruptly to zero

Question 10

A cell of EMF 1.5 V and internal resistance $0.5\ \Omega$ is connected to an external load, supplying a current of 1.0 A. What is the terminal potential difference across the cell?

Accepted Answer

B) 1.0 V

Answer

A) 0.5 V

Answer

C) 1.5 V

Answer

D) 2.0 V

Question 11

Kirchhoff's First Law (Junction Rule) $\sum I = 0$ at any electrical junction is a direct consequence of which fundamental conservation law?

Accepted Answer

B) Conservation of Charge

Answer

A) Conservation of Energy

Answer

C) Conservation of Linear Momentum

Answer

D) Conservation of Mass

Question 12

Kirchhoff's Second Law (Loop Rule) $\sum \Delta V = 0$ around any closed electrical loop is based on which conservation principle?

Accepted Answer

A) Conservation of Energy

Answer

B) Conservation of Charge

Answer

C) Conservation of Angular Momentum

Answer

D) Conservation of Magnetic Flux

Question 13

Mobility $\mu$ of a charge carrier is defined as drift velocity per unit electric field. What is its SI unit?

Accepted Answer

B) m^2 V^-1 s^-1

Answer

A) m / s

Answer

C) V m^-1

Answer

D) C m^-1

Question 14

How is electrical conductivity ($\sigma$) mathematically related to resistivity ($\rho$) of a conductor?

Accepted Answer

B) \sigma = 1 / \rho

Answer

A) \sigma = \rho^2

Answer

C) \sigma = \rho

Answer

D) \sigma = \sqrt{\rho}

Question 15

Consider a Wheatstone bridge circuit consisting of four resistors P, Q, R, and $S$ arranged in order around a quadrilateral loop with a galvanometer across the central bridge branch.

Under what condition is the Wheatstone bridge balanced (zero galvanometer deflection)?

Accepted Answer

B) P / Q = R / S

Answer

A) P + Q = R + S

Answer

C) P \cdot Q = R \cdot S

Answer

D) P - Q = R - S

Question 16

An electric cell of EMF 6.0 V and internal resistance $0.2\ \Omega$ is directly short-circuited by a wire of zero resistance. What is the maximum short-circuit current?

Accepted Answer

C) 30.0 A

Answer

A) 1.2 A

Answer

B) 12.0 A

Answer

D) 60.0 A

Question 17

A steady current of 10 A passes through a conductor with a uniform cross-sectional area of $2.0 imes 10^{-6}m^2$. Calculate the current density $J$ in the conductor.

Accepted Answer

C) 5.0 × 10^6 A/m^2

Answer

A) 5.0 × 10^4 A/m^2

Answer

B) 5.0 × 10^5 A/m^2

Answer

D) 2.0 × 10^7 A/m^2

Question 18

In a potentiometer setup, the potential gradient along the uniform potentiometer wire is $k = 0.02 ext{ V/cm}$. A balance point for an unknown cell is obtained at a length of 250 cm. Find the EMF of the cell.

Accepted Answer

B) 5.0 V

Answer

A) 2.5 V

Answer

C) 10.0 V

Answer

D) 12.5 V

Question 19

When $n$ identical electric cells, each having electromotive force $E$ and internal resistance $r$, are connected in parallel, what is the net equivalent EMF of the combination?

Accepted Answer

C) E

Answer

A) n E

Answer

B) E / n

Answer

D) n^2 E

Question 20

When $n$ identical cells, each having electromotive force $E$ and internal resistance $r$, are connected in series, what is the net total internal resistance of the combination?

Accepted Answer

B) n r

Answer

A) r / n

Answer

C) r

Answer

D) n^2 r