Question 376:

• JAMB 1985

An electric kettle, connected to a 240V mains, produces 6.0 x 10⁵J of heat energy to boil a quantity of water in 5 minutes. Find the resistance of the kettle.

A. 14.4\(\Omega\)
B. 28.8\(\Omega\)
C. 144\(\Omega\)
D. 288\(\Omega\)
E. 2880\(\Omega\)

Question 377:

• JAMB 1985

On which of the following does the operation of a moving coil ammeter depend? i. Electromagnetic induction ii. Force on a carrying-current conductor iii. Magnetic effect of an electric current

A. I only
B. Ii only
C. Iii only
D. Ii and iii only
E. I,ii and iii

Question 378:

• JAMB 1985

Which of the following statements is NOT correct?

A. A galvanometer can be converted to an ammeter with a different range by connecting a high resistance in series
B. An electric current always produces a magnetic field
C. Maxwell's screw rule states that if a corkscrew moves inthe direction of the current, the hand turns in the direction of the lines of force
D. Electromagnets are used in electric bells and telephone recievers
E. The lines of force round a straight current carrying conductor are circular

Question 379:

• JAMB 1985

A transformer has a primary coil with 500 turns and a secondary coil with 2500 turns. When the voltage input to the primary coil is 120V, the output is

A. 6000V
B. 600V
C. 240V
D. 60V
E. 24V

Question 380:

• JAMB 1985

Which of the following statements about electrolysis is NOT correct?

A. The substances in solution in the electrolyte become ionized
B. Ions are electrically charged and are attracted towards electrodes when a potential difference is applied
C. Ions may be discharged at the electrodes, forming bubbles or deposits
D. The mass deposited depends upon the length of time for which current flows
E. The mass of gas set free or metal deposited is proportional to the square of the current