Jamb Physics 2012 Past Questions and Answers

Question 71:

• JAMB 2012

A 2H inductor has negligible resistance and is connected to a 50/Ï€ Hz A.C. Supply. The reactance of the inductor is

A. 200 Ω
B. 50 Ω
C. 100/π Ω
D. 25/π Ω

Question 72:

• JAMB 2012

A cell of internal resistance 1Ω supplies current to an external resistor of 3Ω. The efficiency of the cell is

A. 25%
B. 33%
C. 50%
D. 75%

Question 73:

• JAMB 2012

A conductor of length 2m carries a current of 0.8A while kept in a magnetic field of magnetic flux density 0.5T. The maximum force acting on it is

A. 0.2N
B. 0.8N
C. 3.2N
D. 8.0N

Question 74:

• JAMB 2012

Light of energy 5eV falls on a metal of work function 3eV and electrons are liberated. The stopping potential is

A. 1.7V
B. 2.0V
C. 8.0V
D. 15.0V

Question 75:

• JAMB 2012

The height at which the atmosphere ceases to exist is about 80km. If the atmospheric pressure on the ground level is 760mmHg, the pressure at a height of 20km above the ground level is

A. 380mmHg
B. 570mmHg
C. 190mmHg
D. 480mmHg