Physics Past Questions and Answers

An electric cell has an internal resistance of 2 ohms. A current of 0.5A is found to flow when a resistor of 5 ohms resistance is connected across it. What is the electromotive force of the cell?

A 5 volts
B 3.5 volts
C 2.5 volts
D 1 volts
E 10 volts

Question 22:

Which of the following is the correct definition of 'half-life'?

A The average life-time of a radioactive material
B The time it takes a radioactive material to decay to half of its original quantity
C Half the period a radioactive material decays completely
D Half of the decay constant
E The decay constant times life-time

Question 23:

The bulb of a motorcycle head-lamp is marked 40W, 6V. The resistance of the filament when it is switched on is

A \(\frac{6^2}{40^2}\)ohms
B \(\frac{40}{6^2}\)ohms
C \(\frac{40}{6}\)ohms
D 6 x 40 ohms
E \(\frac{6^2}{40}\)ohms

Question 24:

In an electrolysis experiment, a cathode of mass 5g is found o weigh 5.01g after a current of 5A flows for 50 seconds. What is the electrochemical equivalent of the deposited substance?

A 0.00004g/C
B 0.00002g/C
C 0.02500g/C
D 0.05000g/C
E 0.00001g/C

Question 25:

Which of the following statements about radioactivity are true? i. alpha particle is positively charged ii. Beta particle is negatively charged iii. Gamma ray is neutral iv. Beta particle has the same mass as helium atom v. Gamma ray is charged

A I, ii, iii and iv only
B Iv and v only
C I, ii and iii only
D I, ii and v only
E All