ECAT Physics — Alternating Current
Alternating Current is part of the Physics section of the UET ECAT (30 of the 100 MCQs). It breaks into 4 subtopics, and we hold 31 ECAT-pattern practice MCQs on it, each with a written explanation. Tap a subtopic below to practise just that.
Subtopics (4)
How Alternating Current is tested
Across the 7 ECAT past papers on ParhaiKrlo, Alternating Current accounts for 16 questions. It appears in 6 of them, about 2.7 questions a paper. The heaviest was ECAT Past Paper 07, with 4 questions.
| Paper | Questions |
|---|---|
| ECAT Past Paper 07 | 4 |
| ECAT Past Paper 05 | 3 |
| ECAT Past Paper 04 | 4 |
| ECAT Past Paper 03 | 3 |
| ECAT Past Paper 02 | 1 |
| ECAT Past Paper 01 | 1 |
Alternating Current MCQs from the ECAT past papers
Try each one before opening the answer. Each comes with a short explanation.
- Q1 · ECAT Past Paper 07 · Alternating Current
In frequency modulation, the amplitude of the carrier wave remains the same but its frequency changes in proportion to:
- A.The amplitude of the modulating signal
- B.The sign of the modulating signal
- C.The frequency of the modulating signal
- D.All of these
Show answer
Answer: A. The amplitude of the modulating signal — FM: the carrier's frequency deviation is proportional to the modulating signal's amplitude.
- Q2 · ECAT Past Paper 05 · Alternating Current
A particular radio station is selected by turning the tuning knob of a radio. Turning the knob changes the:
- A.Inductance
- B.Capacitance
- C.Impedance
- D.All
Show answer
Answer: B. Capacitance — The knob turns a variable capacitor, changing the resonant frequency of the LC tuning circuit.
- Q3 · ECAT Past Paper 04 · Alternating Current
Which of the following devices does NOT use electromagnetic waves for its operation?
- A.Ultrasound machine
- B.X-ray machine
- C.Radar
- D.Mobile phone
Show answer
Answer: A. Ultrasound machine — Ultrasound is a high-frequency sound (mechanical) wave, not an electromagnetic wave.