An old man, unable to apply a large force whishes to use screw jack for lifting his car wheels. If L is the length of the rod used to turn the jack and p is the pitch of jack screw, then he should use a jack in which _____.

1. 1. L is small and p is small
   2. L is large and p is large
   3. L is small and p is large
   4. L is large and p is small

The working of the receiver of a telephone depends upon the _____.

1. 1. Efficiency of the loudspeaker which enhances the loudness of sound
   2. Diaphragm which is made to vibrate by the incoming sound wave
   3. Change in magnetization of an electromagnet, which causes a diaphragm to vibrate
   4. Conversion of electric signal, after its amplification into sound wave

Erect and virtual images are always produced by _____.

1. 1. Concave mirrors alone
   2. Plane mirrors alone
   3. Concave and and convex mirrors
   4. Plane and convex mirrors

When a moving bus stops suddenly, the passengers are pushed forward because of the _____.

1. 1. Friction between the passengers and the earth
   2. Inertia of the passengers
   3. Frictions between the earth and the bus
   4. Inertia of the bus

A car and a loaded truck are moving with the same speed along a road. As compared to the truck, the car shall possess _____.

1. 1. More potential energy
   2. More kinetic energy
   3. Less kinetic energy
   4. More mechanical energy

Electronics is the study of _____.

1. 1. Flow of molecules
   2. Flow of photons
   3. Flow of electrons
   4. All of these

Which of the following functions is performed by a photo cell?

1. 1. It converts magnetic energy into electrical energy
   2. It converts chemical energy into electrical energy
   3. It converts electrical energy into light energy
   4. It converts light energy into electrical energy

An electric motor runs on which principle?

1. 1. The current flowing through a conductor causes generation of heat that drives the engine
   2. Changing magnetic field induces an electromotive force in a conductor
   3. A conductor carrying current n the direction perpendicular to the external magnetic field feels a force
   4. Electrical energy can be converted into chemical energy in the presence of magnetic fields

Ball bearings are used to reduce frictions by_____.

1. 1. Reducing the area of contact with the use of metallic balls
   2. Applying lubricants to the balls used
   3. Increasing the area of contact with the use of metallic balls
   4. None of the above

Which one of the following is not an advantage of three phase system of electric power supply over one phase system?

1. 1. The power consumption is less
   2. the output voltage is higher
   3. The total output is almost constant
   4. the output of a 3-phase machine is greater than that of a single phase machine