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

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.

The diagram below shows a magnetic kept just below the conductor AB which is kept in North South direction.

(i) In which direction will the needle deflect when the key is closed ?
(ii) Why is the deflection produced ?
(iii) What will be the change in the deflection if the magnetic needle is taken just above the conductor AB ?
(iv) Name one device which works on this principle.

What is wrong with the circuit diagram (Fig. 34)? Carefully check the symbols and assign proper positive and negative signs to them.

A simple electric circuit has 24 V battery and a resistor of 60 Ω. What will be the current in the circuit? The resistance of the connecting wires is negligible.