Physics Past Questions and Answers

The operation of an optical fibre is based on the principal of

A Dispersion of light
B Interference of light
C Refraction of light
D Polarization of light

Question 27:

I the diagram above, what would happen to the current I, if another resistor, R₂, is connected in parallel to R₁?

A It will increase because the equivalent resistance will increase
B It will decrease if R₂ is greater than R₁
C It will increase because the effective resistance will decrease
D It will decrease if R₂ is less than R₁

Question 28:

A wire of 5Î© resistance is drawn out so that its new length is two times the original length. If the resistivity of the wire remains the same and the cross-sectional area is halved, the new resistance is

A 40Î©
B 20Ω
C 10Î©
D 5Î©

Question 29:

An electron of charge 1.6 x 10^-19C is accelerated between two metal plates. If the kinetics energy of the electron is 4.8 x 10^-17J, the potential difference between the plate is

A 30V
B 40V
C 300V
D 400V

Question 30:

A magnetic field is said to exist at a point if a force is

A Exerted on a stationary charge at the point
B Exerted on a moving charge at the point
C Deflected at the point
D Strengthened at the point