Chapter 4- MCQ Exercise

If a current varies continuously from zero to a maximum value and changes its direction periodically then the current is...

• direct.

• steady.

• alternating.

• repetitive.

A child rubs a plastic ruler on her hair and brings near small bits of paper. The bits of paper are then attracted to the ruler. Which of the following best explains the result?

• Paper is charged due to induction.

• Paper is always attracted towards plastic.

• Paper is naturally a negatively charged material.

• Paper is neutral and the ruler is negatively charged.

Copper sulphate solution, ammonium chloride solution and dilute sulphuric acid are liquid conductors. They conduct electric current due to the movement of....

• neutrons.

• electrons.

• protons.

• ions.

Karma uses a piece of silk cloth to rub a plastic comb. The comb then becomes positively charged because it....

• loses protons.

• gains protons.

• loses electrons.

• gains electrons.

An electrical device that converts electrical energy into mechanical energy is...

• d.c. dynamo.

• d.c. motor.

• transformer.

• electroscope.

When a strong magnet is moved near a copper coil....

• there is no effect on the copper coil.

• voltage is induced across the copper coil.

• copper coil is attracted towards the magnet.

• copper coil is repelled away from the magnet.

When the number of electrons passing through a cross -section of a conductor increases, the electric current through the conductor...

• decreases.

• increases.

• remains same.

• first increases and then decreases.

What is the function of carbon brushes in d.c. motor?

• electricity passes through it and due to magnetic field it experiences a force and rotates.

• it provides uniform magnetic field directed from north pole to south pole

• rotate along with the armature coil.

• kept in contact with the two split rings and they do not rotate along with the split rings.

How much charge passes through a lamp of 3 A in 30 seconds?

Refer example 4.2, Page No. 112

• 10 C

• 90 C

• 9 C

• 33 C

A charge of 10 coulomb passes through a cross-section of a conductor in 20 seconds. What is the magnitude of current flowing through it?

Refer example 4.1, page 111

• 2 A

• 200 A

• 0.5 A

• 5 A