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
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