Physics Past Questions and Answers

The main function of the mouth of a telephone is to convert sound energy into

A Heat energy
B Light energy
C Chemical energy
D Electrical energy
E Mechanical energy

Question 517:

Which of the following is not a component of a d.c. electric motor?

A Commutator
B Field magnets
C Slip rings
D Armature
E Carbon brushes

Question 518:

The diagram above illustrates the conversion of a galvanometer of resistance 29 to an ammeter. The galvanometer gives a full-scale deflection for a current of 10mA. Calculate the value of R.

A 2.0 x 10³ Î©
B 2.0 x 10² Ω
C 2.0 x 10^-1 Î©
D 2.0 x 10^-2 Î©
E 2.0 x 10^-3 Î©

Question 519:

A wire of length 100cm and cross-sectional area of 2.0 x 10^-3cm² has a resistance of 0.10 Î©. Calculate its electrical conductivity.

B 5.0 x 10⁶Ω^-1cm^-1

Question 520:

Lenz's law of electromagnetic induction states that

A E.m.f. is induced in a circuit whenever there is a change in the magnetic flux linked with the circuit.
B The induced current in a conductor is in such a direction as to oppose the change producing it
C The magnitude of the induced e.m.f. in a circuit is proportional to the rate of change of the number of lines of force linking the circuit
D A force is exerted on a current-carrying conductor in a magnetic Held
E The induced charge is constant for a fixed change of flux.