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Wednesday, 28 October 2026
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Physics Past Questions and Answers

Jamb 1979 Physics Questions

Question 21:
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
View Answer & Explanation
Question 22:
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
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Question 23:
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
View Answer & Explanation
Question 24:
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
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Question 25:
Consider a thick glass tumbler and a thin glass tumbler which are made of the same kind of glass. Some hot liquid is poured into them. Which of the following statements is correct?
  • A The thick tumbler is less likely to crack because it is stronger
  • B The thick tumbler is less likely to crack because it insulates the heat beter, glass being a poor conductor of heat
  • C Both tumblers are equally likely to crack because they are made of the same kind of glass
  • D The thick tumbler is more likely to crack because uneven expansion persists for a longer time within the thicker glass
  • E The thick tumbler is more likely to crack because it is heavier
View Answer & Explanation