Aim: To demonstrate that a changing magnetic field can induce an electric current in a nearby conductor.

Apparatus:

• A coil of wire connected to a galvanometer
• A bar magnet
• A track or guide to allow the magnet to move steadily towards and away from the coil

Procedure:

1. Connect the coil of wire to the galvanometer.
2. Place the bar magnet so that it is positioned to move towards and away from the coil.
3. Slowly move the magnet towards the coil. As the magnet approaches the coil, a magnetic field changes in the region around the coil.
4. As the magnetic field changes, an electric current will be induced in the coil, which will be detected by the galvanometer (indicated by a deflection).
5. Repeat the experiment by moving the magnet away from the coil. The galvanometer should show a deflection in the opposite direction.

Explanation: When the magnet moves towards the coil, the magnetic flux through the coil changes. According to Faraday's Law of electromagnetic induction, this change in magnetic flux induces an electromotive force (EMF) in the coil, which drives an electric current. The direction of the induced current is such that it opposes the change in magnetic flux (Lenz's Law). When the magnet moves away, the magnetic flux decreases, inducing a current in the opposite direction.

Formula: The magnetic field strength (B) inside a solenoid is given by the formula:

B = μ₀ * n * I

where:

• μ₀ is the permeability of free space (4π x 10^-7 T m/A)
• n is the number of turns per unit length (number of turns / length of solenoid)
• I is the current (in Amperes)

Calculation:

1. Calculate the number of turns per unit length: n = 100 turns / 0.2 m = 500 turns/m
2. Substitute the values into the formula: B = (4π x 10^-7 T m/A) * (500 turns/m) * (2 A)
3. B = 12.566 x 10^-4 T ≈ 1.26 x 10^-3 T

Answer: The magnetic field strength inside the solenoid is approximately 1.26 x 10^-3 T.

Aim: To investigate the relationship between the number of turns in a coil and the magnitude of the induced current when the coil is moved through a magnetic field.

Apparatus:

• A coil of wire (with a known number of turns, e.g., 50 turns)
• A magnet (e.g., a horseshoe magnet)
• A sensitive galvanometer
• Connecting wires
• A track or guide to ensure the coil moves in a straight line through the magnetic field

Procedure:

1. Connect the coil to the galvanometer using the connecting wires.
2. Position the magnet so that the coil can move through the magnetic field between the poles of the magnet.
3. Slowly move the coil into and out of the magnetic field, keeping the speed constant.
4. Record the reading on the galvanometer for each position of the coil (e.g., when fully in the field, halfway in, fully out).
5. Repeat the experiment several times to obtain reliable results.
6. Use coils with different numbers of turns (e.g., 25, 50, 75 turns) and repeat the procedure for each coil.

Variables:

• Independent variable: The number of turns in the coil.
• Dependent variable: The magnitude of the induced current (measured by the galvanometer reading).
• Controlled variables: The speed of the coil's movement, the strength of the magnet, the distance between the coil and the magnet.

Analysis: Plot a graph of the induced current (galvanometer reading) against the number of turns in the coil. The graph should show a clear relationship between the number of turns and the magnitude of the induced current. Discuss the relationship observed and explain it in terms of Faraday's Law of electromagnetic induction.