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WAEC WASSCE Physics 2012 past questions and answers

This 2012 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 2012 set with instant marking.

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Sample WAEC WASSCE Physics 2012 questions

1. A radioactive sample has a half-life of 8 days. What mass remains from an initial 160 g after 24 days?
  1. 20 g
  2. 40 g
  3. 10 g
  4. 80 g

Answer: A. 20 g

Twenty-four days is three half-lives, so the remaining mass is 160/2^3 = 20 g.

2. A photon has frequency 3.0 x 10^18 Hz; using Planck's constant h = 6.6 x 10^-34 J s, what is its energy?
  1. 2.2 x 10^-16 J
  2. 2.0 x 10^-15 J
  3. 4.5 x 10^-52 J
  4. 9.6 x 10^-16 J

Answer: B. 2.0 x 10^-15 J

The photon energy is hf = 6.6 x 10^-34 x 3.0 x 10^18 = 1.98 x 10^-15 J, approximately 2.0 x 10^-15 J.

3. A silicon p-n junction diode is connected in forward bias; what is its usual effect in a simple circuit?
  1. It blocks current in both directions.
  2. It stores charge without conducting.
  3. It allows substantial current to flow once the forward voltage is sufficient.
  4. It converts direct current into alternating current.

Answer: C. It allows substantial current to flow once the forward voltage is sufficient.

Forward bias reduces the junction barrier, allowing current to flow when the applied voltage is sufficient.

4. An ideal transformer has 500 turns in its primary coil and 100 turns in its secondary coil; if the primary voltage is 240 V, what is the secondary voltage?
  1. 1,200 V
  2. 240 V
  3. 120 V
  4. 48 V

Answer: D. 48 V

For an ideal transformer Vs/Vp = Ns/Np, so Vs = 240 x 100/500 = 48 V.

5. The magnetic flux through each turn of a 100-turn coil changes by 0.060 Wb in 0.020 s; what is the magnitude of the average induced e.m.f.?
  1. 300 V
  2. 30 V
  3. 0.30 V
  4. 3,000 V

Answer: A. 300 V

Faraday's law gives E = N(change in flux)/time = 100 x 0.060/0.020 = 300 V.

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