Physics Past Questions and Answers

Energy losses through eddy currents are reduced by using

A Low resistance wires
B Insulated soft iron wires
C Few turns of wires
D High resistance wires

Question 112:

A capacitor of 20 x 10^-12F and an inductor are joined in series. The value of the inductance that will give the circuit a resonance frequency of 200kHz is

A I/16 H
B I/8 H
C I/64 H
D I/32 H

Question 113:

The magnetic force on a charged particle moving with velocity v is

A Proportional to both the magnitude of the charge and the velocity v
B Independent of the magnitude of the charge
C Proportional to the velocity v only
D Proportional to the magnitude of the charge only

Question 114:

A copper cube weighs 0.25 N in air, 0.17N when completely immersed in paraffin oil and 0.15 N when completely immersed in water.The ratio of upthrust in oil to upthrust in water is

A 3 : 5
B 4 : 5
C 7 : 10
D 13 : 10

Question 115:

A wheel and axle is used to raise a load of 500 N by the application of an effort of 250 N. If the radii of the wheel and the axle are 0.4 cm and 0.1 cm respectively, the efficiency of the machine is

A 20 %
B 40 %
C 50 %
D 60 %