1 Marks Question

Question 11 Mark

Would you prefer a voltmeter or a potentiometer to measure the emf of a battery?

Answer

Because potentiometer doesn't draw any current for itself from the primary circuit and hence gives more accurate measurement thereby acting as an ideal voltmeter. It uses null method to measure.

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Question 21 Mark

Is work done by a battery always equal to the thermal energy developed in electrical circuit? What happens if a capacitor is connected in the circuit?

Answer

No, the work done by a battery is not always equal to the thermal energy developed in the electrical circuit. In case of a non-ideal battery, the work done by the battery is the sum of the thermal energy developed in the electric circuit and the thermal energy developed in the internal resistance of the battery. $12 \mathrm{C} \mathrm{V}^2$ of energy is lost in the form of heat and electromagnetic radiation.

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Question 31 Mark

Does a conductor become charged when a current is passed through it?

Answer

Yes as charge passes through it is is charged. For example we use electrical magnets in some equipment.

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Question 41 Mark

Sometimes it is said that "heat is developed" in a resistance when there is an electric current in it. Recall that heat is defined as the energy being transferred due to temperature difference. Is the statement in quotes technically correct?

Answer

Yes both statements are correct.

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Question 51 Mark

We often say, "A current is going through the wire." What goes through the wire, the charge or the current?

Answer

Only charge goes from the wire, rate of flow of charge is known as current.

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Question 61 Mark

The thermal energy developed in a current-carrying resistor is given by $U = i^2$ Rt and also by U = Vit. Should we say that U is proportional to $i^2$ or i?

Answer

As the simplest form is $= i^2Rt$
So, U is directly proportional to $i^2$.

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Question 71 Mark

One of your friends argues that he has read in the previous chapters that there can be no electric field inside a conductor. And hence there can be no current through it. What is the fallacy of this argument?

Answer

If there can be no current inside a conductor there can be current on its surface so "there can be no current through it" is wrong.

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Question 81 Mark

The drift speed is defined as $\text{v}_\text{d}=\frac{\Delta\text{l}}{\Delta\text{t}}$ where $\Delta\text{l}$ is the distance drifted in a long time $\Delta\text{t}.$ Why don't we define the drift speed as the limit of $\frac{\Delta\text{l}}{\Delta\text{t}}\ \text{as}\ \Delta\text{t}\rightarrow0?$

Answer

As electron doesn't travel linearly so we need to calculate average time thus we need to consider drift distance for long time. That can not be calculated in case of t → 0.

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Question 91 Mark

A fan with copper winding in its motor consumes less power as compared to an otherwise similar fan aluminium winding. Explain.

Answer

As the copper has higher conductance than aluminum so there is low power loss thus it consumes lesser power.

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Question 101 Mark

Suppose you have three resistors, each of value $30\Omega.$ List all the different resistances you can obtain using them.

Answer

All in series.
All in parallel.
Two parallel and one in series.

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Question 111 Mark

When a current is established in a wire, the free electrons drift in the direction opposite to the current. Does the number of free electrons in the wire continuously decrease?

Answer

No the complete circuit (which is the only condition to flow current) restores number of electrons equal to the number of electrons passed through wire.

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Question 121 Mark

In a TV tube, electrons are accelerated from the rear to the front. What is the direction of the current?

Answer

Direction of current is in opposite direction of electron moving thus the current is from front to rear.

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