MDCAT Physics chapter 13: Physics · Physics of solids and electronics MCQs with answers

By Team Megalecture · Updated 4 Nov 2026

20 exam-style questions on Physics · Physics of solids and electronics, each with the answer and a short explanation. Ten of them are below to try. The chapter test draws ten fresh questions each time and is marked the moment you finish, with your score by topic.

20 questions · 2 topics · 10 per test

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What chapter 13 covers

Ten Physics · Physics of solids and electronics questions with answers

Try each one, then open the answer. These ten stay the same; the test draws new ones every time.

1. A wire is stretched by 2.0 mm as the force on it rises steadily from zero to 50 N, within the proportional limit. The elastic potential energy stored in the wire is

  1. A
    0.10 J
  2. B
    50 J
  3. C
    0.050 J
  4. D
    0.025 J
Show answer

Answer: C. Energy stored = area under the force–extension line = ½F(ΔL) = ½ × 50 × 2.0 × 10−3 = 0.050 J. Leaving out the ½, as if the full 50 N acted throughout, gives 0.10 J, and not converting mm to m gives 50 J.

2. A p-n junction is forward biased when

  1. A
    its n-region is joined to the positive terminal of the battery
  2. B
    the applied voltage makes the depletion region wider
  3. C
    its p-region is joined to the positive terminal of the battery
  4. D
    the applied voltage adds to the junction potential barrier
Show answer

Answer: C. Joining p to + and n to − pushes holes and electrons towards the junction, narrowing the depletion region and lowering the barrier, so a large current flows. A wider depletion region and a higher barrier are the signs of reverse bias.

3. An exclusive-OR (XOR) gate with two inputs gives an output of 1 when

  1. A
    its two inputs are both 1
  2. B
    its two inputs are different
  3. C
    its two inputs are both 0
  4. D
    its two inputs are identical
Show answer

Answer: B. XOR gives 1 for inputs 0, 1 and 1, 0, and gives 0 for 0, 0 and 1, 1: its output is 1 only when the inputs differ. An XNOR gate gives 1 when the inputs are the same.

4. A silicon diode (potential barrier 0.7 V) is forward biased in series with a 1.0 kΩ resistor across a 5.7 V battery. The current in the circuit is

  1. A
    5.0 mA
  2. B
    5.7 mA
  3. C
    6.4 mA
  4. D
    0.7 mA
Show answer

Answer: A. About 0.7 V is used across the silicon junction, leaving 5.7 − 0.7 = 5.0 V across the resistor: I = 5.0 V ÷ 1.0 kΩ = 5.0 mA. Ignoring the barrier gives 5.7 mA, and adding it gives 6.4 mA.

5. A piece of n-type silicon, taken as a whole, is

  1. A
    negatively charged
  2. B
    positively charged
  3. C
    charged only while a current flows
  4. D
    electrically neutral
Show answer

Answer: D. n-type silicon has extra free electrons, but each one comes from a neutral donor atom (such as arsenic) that is left as a fixed positive ion, so the total charge is zero. The "n" describes the majority charge carriers, not the net charge.

6. In a full-wave bridge rectifier made of four diodes, how many diodes conduct during each half cycle of the input?

  1. A
    1
  2. B
    3
  3. C
    2
  4. D
    4
Show answer

Answer: C. In each half cycle one pair of opposite diodes is forward biased and the other pair reverse biased, so two diodes conduct at a time and the pairs take turns. Both halves of the input then drive current the same way through the load.

7. For a transistor to work as an amplifier, its junctions must be biased so that

  1. A
    base–emitter is reverse biased and collector–base is forward biased
  2. B
    base–emitter is forward biased and collector–base is reverse biased
  3. C
    both the base–emitter and collector–base junctions are forward biased
  4. D
    both the base–emitter and collector–base junctions are reverse biased
Show answer

Answer: B. The forward-biased base–emitter junction injects charge carriers into the thin base, and the reverse-biased collector–base junction sweeps nearly all of them into the collector. Both junctions forward biased is saturation and both reverse biased is cut-off, the two states used when a transistor acts as a switch.

8. A transistor used as a switch is in its OFF state. It is then

  1. A
    saturated, with almost no collector current
  2. B
    cut off, with the largest collector current
  3. C
    cut off, with almost no collector current
  4. D
    saturated, with the largest collector current
Show answer

Answer: C. With no forward bias on the base–emitter junction, IB ≈ 0 and so IC ≈ 0: the transistor is cut off and acts as an open switch, with nearly all the supply voltage across it. Saturation, with the largest collector current, is the ON state.

9. In a good conductor such as copper, the valence band and the conduction band

  1. A
    overlap, so free electrons are always present
  2. B
    are separated by a very wide forbidden energy gap
  3. C
    are separated by a gap of about 1 eV
  4. D
    are both completely filled with electrons
Show answer

Answer: A. In metals the bands overlap, so many electrons are free to move even at low temperatures. A wide forbidden gap is typical of insulators, and a gap of about 1 eV of semiconductors.

10. On the stress–strain curve of a ductile metal, the point beyond which the wire no longer returns to its original length when the load is removed is the

  1. A
    proportional limit
  2. B
    ultimate tensile strength
  3. C
    breaking point
  4. D
    elastic limit
Show answer

Answer: D. Up to the elastic limit the deformation disappears when the load is removed; beyond it the metal undergoes plastic deformation and keeps a permanent extension. The proportional limit, slightly lower on the curve, is where stress stops being proportional to strain.

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Physics · Physics of solids and electronics: questions students ask

How many Physics · Physics of solids and electronics MCQs are there?

20, each with the answer and a short explanation, across 2 topics: Properties of solids, Electronics. Every chapter test draws ten of them, so you can take it many times.

Is the MDCAT Physics chapter 13 test free?

Yes. The test, the answers and the explanations are free and need no sign-up. Sign in only if you want your scores kept across devices.

How is the chapter test marked?

The moment you press Finish: your score, the right answer and an explanation for every question, and the ones you got wrong saved in My mistakes to retry.

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