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Punjab (PTB) · Chapter test · Free

2nd Year Physics Chapter 5 TestALTERNATING CURRENT

30 marks · 40 minutes · 21 questions. Covers: CHAP 17: ALTERNATING CURRENT.

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2nd Year Physics Chapter 5 Test

2nd Year · Physics · Punjab (PTB)

Name: ____________Roll No: ________Class/Section: ________Date: ________Total marks: 30Time: 40 minutes

Q1. Multiple choice questions (Attempt all · 10 × 1 = 10)

  1. Through which of the AC-circuit elements both emf and current are in phase?

    1. Resistance

    2. Inductor

    3. Capacitor

    4. LED

  2. An alternating current (AC) varies sinusoidally and can be represented by time-dependent:

    1. Linear functions

    2. Sine or cosine functions

    3. Logarithmic functions

    4. Exponential functions

  3. Power dissipation in a purely resistive AC circuit is directly proportional to the:

    1. Square of the current

    2. Square root of the current

    3. Inverse of the current

    4. Square of the resistance

  4. Name of device that is used as a part of charging circuit for mobile phones is:

    1. Full-wave bridge rectifier

    2. Half-wave rectifier

    3. AC generator

    4. Battery

  5. A periodically varying current is alternating if its two half-cycles are:

    1. Unequal in time

    2. Both positive

    3. Exactly symmetrical (one positive, one negative)

    4. Both negative

  6. Which of the following are the basic circuit elements in an AC circuit?

    1. Resistor only

    2. Resistor and Inductor only

    3. Capacitor and Inductor only

    4. Resistor, Inductor, and Capacitor

  7. A capacitor is plugged into a 110 Vrms voltage source, 60 Hz voltage source with an ammeter in series. The value of Irms that passes through the capacitor is:

    1. 0.0415 A

    2. 0.415 A

    3. 415 A

    4. 0.0415 A

  8. Because voltage and current are in phase in a resistive AC circuit, their vector representations are drawn:

    1. Perpendicular to each other

    2. Parallel to each other

    3. Anti-parallel to each other

    4. None of these

  9. At resonance, the total impedance (Z) of a series RLC circuit becomes:

    1. Maximum

    2. Minimum and equal to resistance

    3. Infinite

    4. Zero

  10. When converting DC power into AC power, we must factor in the efficiency of the:

    1. Inductor

    2. Transformer

    3. Inverter

    4. Generator

Q2. Short questions (Attempt any 6 of 8 · 6 × 2 = 12)

  1. Explain how an induction cooktop uses a parallel RLC circuit to heat metal cookware.

  2. Name four real-world devices or fields where mutual inductance finds practical applications.

  3. Explain how resistance affects oscillations in an RLC circuit using its mechanical analogy.

  4. Why does a capacitor block DC but allow AC to pass?

  5. How does resistance influence the Q-factor in a parallel RLC circuit?

  6. What is the relationship between frequency (f) and time period (T)? State their units.

  7. What is meant by 'Initial Phase'?

  8. What is the basic circuit element in a DC circuit, and what formula defines its behavior?

Q3. Long questions (Attempt any 2 of 3 · 2 × 4 = 8)

  1. A 50 Hz AC of peak value 1 A flows through primary coil of a transformer. If the mutual inductance between the primary and secondary be 1.5 H, then find the mean value of induced voltage.

  2. A choke coil is needed to operate a lamp at 160 Vrms and 50 Hz. The lamp has an resistance of when running at 10 Arms. Calculate the inductance of the choke coil.

  3. Explain the behaviour of a capacitor in an AC circuit. Derive the expression for capacitive reactance and discuss why current leads the voltage by 90o or .