Electromagnetic induction and Alternative current NEET Exam mcqs

Here are some JEE (Joint Entrance Examination) Main level multiple-choice questions on electromagnetic induction and alternating current:

**Electromagnetic Induction:**

**Question 1:**
When the magnetic flux linked with a closed loop changes, an emf is induced in the loop. This phenomenon is known as:
a) Ampere’s Law
b) Faraday’s Law of Electromagnetic Induction
c) Lenz’s Law
d) Gauss’s Law

**Answer 1:**
b) Faraday’s Law of Electromagnetic Induction

**Question 2:**
An emf is induced in a loop of wire when the magnetic field through it changes. Which of the following will not induce an emf?
a) Moving the loop through a magnetic field
b) Changing the orientation of the loop in a constant magnetic field
c) Changing the current passing through the loop
d) Changing the strength of the magnetic field

**Answer 2:**
c) Changing the current passing through the loop

**Question 3:**
A coil with 200 turns is placed in a magnetic field. If the magnetic flux through each turn is 0.02 Wb, the total flux linkage is:
a) 200 Wb
b) 4 Wb
c) 0.02 Wb
d) 40 Wb

**Answer 3:**
b) 4 Wb

**Question 4:**
The negative sign in Lenz’s law signifies that:
a) Induced emf is always negative
b) Induced current opposes the change in magnetic flux
c) Induced current is always negative
d) Induced emf is in the opposite direction of the magnetic field

**Answer 4:**
b) Induced current opposes the change in magnetic flux

**Question 5:**
A circular loop of wire is placed in a magnetic field perpendicular to the plane of the loop. If the magnetic field increases, the induced current in the loop will flow:
a) Clockwise
b) Counterclockwise
c) Along the diameter
d) There will be no induced current

**Answer 5:**
a) Clockwise

**Alternating Current:**

**Question 6:**
In an AC circuit, the instantaneous current is given by I(t) = I₀ sin(ωt), where I₀ is the maximum current amplitude and ω is the angular frequency. The time taken for the current to go from zero to its maximum value is:
a) π/2 ω
b) π ω
c) 2π/ω
d) π/ω

**Answer 6:**
a) π/2 ω

**Question 7:**
In an AC circuit, the power dissipation is given by P(t) = P₀ sin²(ωt), where P₀ is the maximum power. The average power over a complete cycle is:
a) 0
b) P₀
c) P₀/2
d) P₀/π

**Answer 7:**
c) P₀/2

**Question 8:**
The reactance of a capacitor in an AC circuit:
a) Increases with frequency
b) Decreases with frequency
c) Remains constant with frequency
d) Is not affected by frequency

**Answer 8:**
a) Increases with frequency

**Question 9:**
In an AC circuit containing only a resistor and an inductor in series, the phase difference between the current and the voltage is:
a) 0°
b) 45°
c) 90°
d) 180°

**Answer 9:**
c) 90°

**Question 10:**
In an ideal inductor, the phase difference between the current and the voltage is:
a) 0°
b) 45°
c) 90°
d) 180°

**Answer 10:**
c) 90°