Physics Past Questions and Answers

If the maximum voltage across a 100ohms resistor is 20V, then the maximum power it can dissipate is

A 5.00W
B 4.00W
C 2.00W
D 25W

Question 37:

Which of the following is required to convert a milliammeter to an ammeter?

A A high resistance in parallel
B A high resistance in series
C A low resistance in parallel
D A low resistance in series

Question 38:

The primary winding of a transformer has 400 turns and its secondary has 100 turns. If a source of e.m.f. of 12V is applied to the primary, the secondary e.m.f. will be

A 3V
B 6V
C 24V
D 48V

Question 39:

A light of energy 5eV falls on a metal and the electrons with a maximum kinetic energy of 2eV are ejected. The work function of the metal is

A 0.4eV
B 2.5eV
C 3.0eV
D 7.0eV

Question 40:

The half-life of a radio-active element is 9 days, what fraction of atoms has decayed in 36 days?

A \( \frac{1}{16} \)
B \( \frac{1}{4} \)
C \( \frac{1}{2} \)
D \( \frac{15}{16} \)