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1
MCQ (Single Correct Answer)

Consider a current carrying wire (current $I$ ) in the shape of a circle.

A
source of emf
B
electric field produced by charges accumulated on the surface of wire
C
the charges just behind a given segment of wire which push them just the right way by repulsion
D
the charges ahead
2
MCQ (Single Correct Answer)

Two batteries of emf $\varepsilon_1$ and $\varepsilon_2\left(\varepsilon_2>\varepsilon_1\right)$ and internal resistances $r_1$ and $r_2$ respectively are connected in parallel as shown in figure.

A
Two equivalent emf $\varepsilon_{\mathrm{eq}}$ of the two cells is between $\varepsilon_1$ and $\varepsilon_2, i$.e., $\varepsilon_1<\varepsilon_{\mathrm{eq}}<\varepsilon_2$
B
The equivalent emf $\varepsilon_{\text {eq }}$ is smaller than $\varepsilon_1$
C
The $\varepsilon_{\text {eq }}$ is given by $\varepsilon_{\text {eq }}=\varepsilon_1+\varepsilon_2$ always
D
$\varepsilon_{\text {eq }}$ is independent of internal resistances $r_1$ and $r_2$
3
MCQ (Single Correct Answer)

A resistance $R$ is to be measured using a meter bridge, student chooses the standard resistance $S$ to be $100 \Omega$. He finds the null point at $I_1=2.9 \mathrm{~cm}$. He is told to attempt to improve the accuracy. Which of the following is a useful way?

A
He should measure $I_1$ more accurately
B
He should change $S$ to $1000 \Omega$ and repeat the experiment
C
He should change $S$ to $3 \Omega$ and repeat the experiment
D
He should given up hope of a more accurate measurement with a meter bridge
4
MCQ (Single Correct Answer)

Two cells of emfs approximately 5 V and 10 V are to be accurately compared using a potentiometer of length 400 cm.

A
The battery that runs the potentiometer should have voltage of 8 V
B
The battery of potentiometer can have a voltage of 15 V and $R$ adjusted so that the potential drop across the wire slightly exceeds 10 V
C
The first portion of 50 cm of wire itself should have a potential drop of 10 V
D
Potentiometer is usually used for comparing resistances and not voltages
5
MCQ (Single Correct Answer)

A metal rod of length 10 cm and a rectangular cross-section of $1 \mathrm{~cm} \times \frac{1}{2} \mathrm{~cm}$ is connected to a battery across opposite faces. The resistance will be

A
maximum when the battery is connected across $1 \mathrm{~cm} \times \frac{1}{2} \mathrm{~cm}$ faces
B
maximum when the battery is connected across $10 \mathrm{~cm} \times 1 \mathrm{~cm}$ faces
C
maximum when the battery is connected across $10 \mathrm{~cm} \times \frac{1}{2} \mathrm{~cm}$ faces
D
same irrespective of the three faces
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