(English Medium) ICSE Class 10 - CISCE Question Bank Solutions for Physics

State two ways through which the strength of an electromagnet can be increased.

Complete the following sentence :
……… energy is converted into …………energy by an electric motor.

State two factors on which the magnitude of induced e.m.f. depend.

Name the phenomenon ?

Explain why an induced current must flow in such a direction so as to oppose the change producing it.

Explain the significance of Lenz’s law to show the conservation of energy in electromagnetic induction.

The following diagram in Fig.10.42 shows a coil of several turns of copper wire connected to a sensitive centre zero galvanometer G near a magnet NS. The coil is free to move in the direction shown in the diagram.

(i) Describe the observation if the coil is rapidly moved.
(ii) How would the observation be altered if (a) the coil has twice as many turns (b the coil was made to move three times as fast?

The following diagram in Fig. 10.44 shows a coil X connected to a sensitive centre –zero galvanometer G and a coil P connected to a battery through a switch S.

(a) Describe the observation when the switch S is (i) closed suddenly, (ii) then kept closed, (iii) finally opened.
(b) Name and state the law which explains the above observations.

For what purpose are the transformers used? Can they be used with a direct current source?

How are the e.m.f in the primary and secondary coils of a transformer related with the number of turns in these coils?

The secondary windings of a transformer in which the voltage is stepped down are usually made of thicker wire than the primary. Explain why.

Why is the iron core of a transformer made laminated (thin sheets) instead of being in one solid piece?

The transformer is used in ______ current circuits.

In a transformer, the frequency of A.C. voltage ______. 

What is the function of a transformer in an a.c. circuit? How do the input and output powers in a transformer compare?

Name two kind of energy loss in a transformer. How is it minimized?

The primary coil of a transformed has 800 urns and the secondary coil has 8 turns. It is connected to a 220 V a.c. supply. What will be the output voltage?

A transformer is designed to work from a 240 V a.c. mains and to give a supply of 8 V to ring a house bell. The primary coil has 4800 turns. How many turns will be in the secondary coil?

The input and output voltage of a transformer are 220 V and 44 V respectively. Find:  the turns ratio.

The diagram above shows a circuit with the key k open. Calculate :
(i) the resistance of the circuit when the key k is open.
(ii) the current drawn from the cell when the key k is open.
(iii) the resistance of the circuit when the key k is closed.
(iv) the current drawn from the cell when the key k is closed.