Physics Past Questions and Answers

Calculate the length of a constantan wire of cross- sectional area 4 Ï€ x 10^-8m² and resistivity 1.1 x 10^-6 Î© m required to construct a standard resistor of resistance 21 Î©. [Take Ï€ = 22/7]

A 0.42m
B 2.40 m
C 6.25 m
D 183.75 m
E 590.00 m

Question 282:

In a domestic circuit, electrical appliances and lamps are arranged in parallel across the mains so as to enable the

A Same current to flow through the electrical appliances and the lamps
B Maximum energy to be consumed at least cost
C Same fuse to be used for the electrical appliances and the lamps
D Voltage across the appliances not to be affected when the lamps are switched on and off
E Heat losses to be minimized

Question 283:

Calculate the time in which 4.8 kJ of energy would be expended when an electric heater of resistance 1.8 x 10³Î© is used on a 240 V mains supply. (Neglect heat losses to the surrounding).

A 150.0s
B 90.0s
C 36.0s
D 20.0s
E 2.7s.

Question 284:

Lenz’s law of electromagnetic induction states that

A Electromotive force 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 induced e.m.f. in a circuit is proportional to the rate of change of number of lines of force linking the circuit
D A force is exerted on a current carrying conductor in a magnetic field
E The induced e.m.f. is proportional to the current producing the magnetic flux.

Question 285:

Which of the following statements is not correct?

A A magnetic Held is a region where a magnetic force can be detected.
B Magnetic fields are scalar quantities.
C The magnitude of the magnetic force experienced by a moving charge depends on the speed on the charge.
D The angle between the direction of the earthâ€™s magnetic held and the horizontal is called the angle of dip.
E Iron filings can be used to trace out the magnetic field around a bar magnet.