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WAEC WASSCE Physics 2015 past questions and answers

This 2015 WAEC WASSCE Physics set has 40 practice questions. Try these 5 free sample questions, tap a question to reveal the answer and explanation. Then practise the whole 2015 set with instant marking.

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Sample WAEC WASSCE Physics 2015 questions

1. A radioactive sample has a mass of 80 mg and a half-life of 6 hours. What mass remains after 18 hours?
  1. 10 mg
  2. 20 mg
  3. 40 mg
  4. 5 mg

Answer: A. 10 mg

Eighteen hours is three half-lives, so the mass falls successively from 80 mg to 40 mg, 20 mg and 10 mg.

2. In beta-minus decay, what happens to the proton number Z and nucleon number A of the nucleus?
  1. Z decreases by 1 and A decreases by 1
  2. Z increases by 1 and A remains unchanged
  3. Z remains unchanged and A decreases by 4
  4. Z decreases by 2 and A decreases by 4

Answer: B. Z increases by 1 and A remains unchanged

A neutron changes into a proton and an electron, increasing Z by one while leaving A unchanged.

3. A photon has a frequency of 5.0 x 10^14 Hz. If Planck's constant is 6.6 x 10^-34 J s, what is its energy?
  1. 3.3 x 10^-20 J
  2. 3.3 x 10^-18 J
  3. 3.3 x 10^-19 J
  4. 6.6 x 10^-19 J

Answer: C. 3.3 x 10^-19 J

Using E = hf gives (6.6 x 10^-34)(5.0 x 10^14) = 3.3 x 10^-19 J.

4. What is the main function of a semiconductor diode in a simple circuit?
  1. To store charge permanently
  2. To increase the frequency of an alternating supply
  3. To convert electrical energy directly into sound
  4. To allow current mainly in one direction

Answer: D. To allow current mainly in one direction

A diode conducts readily when forward biased and largely blocks current when reverse biased.

5. A transistor has a collector current of 12 mA and a base current of 0.20 mA. What is its current gain?
  1. 60
  2. 2.4
  3. 12.2
  4. 0.017

Answer: A. 60

The current gain is collector current divided by base current, giving 12/0.20 = 60.

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