Physics Past Questions and Answers

A transformer has 400 turns and 200 turns in the primary and secondary windings respectively. If the current in the primary and secondary windings are 3A and 5A respectively. calculate the efficiency of the transformer?

A 85.0%
B 83.3%
C 37.5%
D 30.0%

Question 3077:

A freely-suspended magnet swinging in a horizontal plane comes to rest with its axis pointing approximately

A North-south
B South-west
C North-east
D South-east

Question 3078:

Calculate the inductance L, of the coil in the circuit diagram shown above

A 3.8H
B 0.6H
C 0.4H
D 0.2H

Question 3079:

In a model of the hydrogen atom, the energy levels W_n are given by the formula W_n = -\(\frac{R}{n^2}\), where n is an integer and R is a constant. Determine the energy released in the transition from n = 3 to n = 2.

A \(\frac{R}{5}\)
B -\(\frac{R}{4}\)
C \(\frac{5R}{36}\)
D \(\frac{-5R}{36}\)

Question 3080:

If a radioactive atom emits a beta particle, Its mass number

A Increases by one
B Remains the same
C Decreases by one
D Increases by two