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

 Can a transformer work when it is connected to a D.C. source? Give a reason.

Draw a simple labeled diagram of a step-down transformer.

Draw a simple labeled diagram of a step-up transformer.

The diagram 10 shows two coils X and Y. The coil X is connected to a battery S and a key K. The coil Y is connected to a galvanometer G.

When the key K is closed. State the polarity
(i)At the end of the coil X,
(ii)At the end C of the coil Y,
(iii)At the end C of the coil Y if the coil Y is (a) Moved towards the coil X, (b) Moved away from the coil X.

The following diagram shows a fixed coil of several turns connected to a center zero galvanometer G and a magnet NS which can move in the direction shown in the diagram.

1. Describe the observation in the galvanometer if
   1. The magnet is moved rapidly,
   2. The magnet is kept still after it has moved into the coil
   3. The magnet is then rapidly pulled out the coil.
2. How would the observation in (i) of part (a) change if a more powerful magnet is used?

Draw and label the diagram of a simple D.C. motor.
(a) Explain the rotation of the coil, giving a reason for your answer.
(b) How can you reverse the direction of rotation of the armature?
(c) How can you increase the speed of rotation of the motor?

Fig. shows a simple form of an A.C. generator.

(a) Name the parts labeled A and B.
(b) What would be the effect of doubling the number of turns on the coil if the speed of rotation remains unchanged?
(c) Which of the output terminals is positive if the coil is rotating in the
direction shown in the diagram (anticlockwise)?
( d ) What is the position of the rotating coil when p.d. across its ends is zero? Explain why p.d. is zero when the coil is at this position .
(e) Sketch a graph showing how the p.d. across the ends of the rotating coil varies with time for an A.C. dynamo.
( f) On th e same sheet of paper and vertically below the first graph using the same time scale, sketch graphs to show the effect of
(i) Doubling the speed of rotation and at the same time keeping
the field and the number of turns constant,
(ii ) Doubling the number of turns on the coil and at the same time
doubling the speed of rotation of the coil, keeping th e speed
constant.

Fill in the blanks by writing (i) Only soft iron, (ii) Only steel, (iii) Both soft-iron and steel for the material of core and/or magnet.

 D.C. motor ______.

Fill in the blanks by writing (i) Only soft iron, (ii) Only steel, (iii) Both soft-iron and steel for the material of core and/or magnet.

A. C. generator______.

Fill in the blanks by writing (i) Only soft iron, (ii) Only steel, (iii) Both soft-iron and steel for the material of core and/or magnet.

Transformer______.

A transformer has 400 turns in the primary winding and 10 turns in the secondary winding. The primary e.m.f. is 250 V and the primary current is 2.0 A. calculate:
(a) The secondary voltage,
(b) The secondary current, assuming 100% efficiency.

Complete the following diagram of a transformer and name the parts labeled A and B. Name the part you have drawn to complete the diagram . What is the material of this part? In this transformer a step-up or step-down? Why?

Show that the quantity 2K/v² has the unit of mass, where K is the kinetic energy of the body.

Two bodies A and B of masses m and M (M ≫ m) have same kinetic energy. Which body will have more momentum?

A pebble is thrown up. It goes to a height and then comes back on the ground. State the different changes in form of energy during its motion.

Name the form of energy in which potential energy can change.

A body of mass 5 kg falls from a height of 10 m to 4 m. Calculate: 

The total energy possessed by the body at any instant? (Take g = 10 ms^-2).

Calculate the decrease in the kinetic energy of a moving body if its velocity reduces to half of the initial velocity.

A ball of mass 0.5 kg slows down from a speed of 5m/s^-1 to that of 3m/s^-1. Calculate the change in kinetic energy of the ball.