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
6
MCQ (Single Correct Answer)
Which of the following characteristics of electrons determines the current in a conductor?
A
Drift velocity alone
B
Thermal velocity alone
C
Both drift velocity and thermal velocity
D
Neither drift nor thermal velocity
7
MCQ (Multiple Correct Answer)
Kirchhoff's junction rule is a reflection of
A
conservation of current density vector
B
conservation of charge
C
the fact that the momentum with which a charged particle approaches a junction is unchanged (as a vector) as the charged particle leaves the junction
D
the fact that there is no accumulation of charges at a junction
8
MCQ (Multiple Correct Answer)
Consider a simple circuit shown in figure stands for a variable resistance $R^{\prime} \cdot R^{\prime}$ can vary from $R_0$ to infinity. $r$ is internal resistance of the battery $(r<< R< R$,$) .$
A
Potential drop across $A B$ is nearly constant as $R^{\prime}$ is varied
B
Current through $R^{\prime}$ is nearly a constant as $R^{\prime}$ is varied
C
Current $I$ depends sensitively on $R^{\prime}$
D
$I \geq \frac{V}{r+R}$ always