Galvanometer

A galvanometer is a sensitive instrument used to detect and measure small electric currents. It operates on the same principle as an electric motor, where a current-carrying coil placed in a magnetic field experiences a force, causing it to rotate. This rotation is proportional to the magnitude of the current.

Galvanometer

Working Principle:

• A coil is placed between the poles of a magnet and is connected to a pointer.
• When a small current flows through the coil, it experiences a torque due to the magnetic field, causing it to rotate.
• The pointer deflects on the galvanometer scale, indicating the current’s presence and magnitude.
• The deflection direction depends on the current flow direction, allowing it to detect both positive and negative currents.
• Voltmeters and Ammeters are based on the galvanometer principle.

1. Aim: To demonstrate electromagnetic induction by moving a conductor in a magnetic field and observe the production of current.

2. Requirements: a copper wire, a strong bar magnet, a galvanometer, two vertical stands with clamps, and connecting wires.

3. Procedure:

• Suspend a copper wire between two vertical stands.
• Connect the copper wire to a galvanometer to detect current.
• Place the bar magnet upright below the wire, with its north or south pole facing up.
• Move the wire horizontally from A to B (perpendicular to the magnetic field). Observe the deflection in the galvanometer.
• Keep the wire stationary and move the magnet instead. Observe the galvanometer again.

If a conducting wire is kept moving in a magnetic field, a current is produced in it.

4. Conclusion: The deflection in the galvanometer indicates that a current is induced in the conductor when it moves in a magnetic field or when the magnetic field changes around it. This confirms Faraday’s Law of Electromagnetic Induction, which states that a changing magnetic field induces an electromotive force (EMF) in a conductor.

1. Aim: To study electromagnetic induction due to a solenoid coil by observing induced current in a nearby coil.

2. Requirements: a solenoid coil, a separate coil connected to a galvanometer, a battery, a switch (plug key), and connecting wires.

3. Procedure

Step 1: Connect the solenoid coil to a battery and switch as shown in Figure (a). Connect a separate coil to a galvanometer to detect induced current.

Step 2: Switch ON/OFF the current in the solenoid coil and observe the deflection in the galvanometer. The galvanometer pointer deflects momentarily when the current is switched ON or OFF, then returns to zero.

Step 3: Keep the solenoid coil energised and move it laterally with respect to the coil (Figure b). The galvanometer shows deflection, indicating an induced current.

Step 4: Keep the solenoid coil energised and move it longitudinally towards or away from the coil (Figure c). The galvanometer deflects, and faster movement results in greater deflection.

(a) When the current in the solenoid coil is switched on or off

(b) when a current is passing through the solenoid coil and the coil is displaced laterally with respect the coil

(c) When a current passing through the solenoid coil and the solenoid coil is displaced longitudinally with respect to the coil

4. Conclusion

• A changing magnetic field induces a current in the coil. 
• Even if the solenoid is stationary, changing the current in the solenoid induces a current in the coil.
• Moving the solenoid laterally or longitudinally with respect to the coil also induces a current.
• Faster motion results in greater induced current.
• This experiment confirms Faraday’s Law of Electromagnetic Induction, stating that a changing magnetic field produces an electromotive force (EMF) in a nearby conductor.

1. It is used in analogue measuring instruments like ammeters and voltmeters to measure current and voltage.
2. Detects small electric currents in a circuit, including their magnitude and direction.
3. It is used in Wheatstone bridge circuits to determine unknown resistance.
4. Helps in testing electrical circuits for faults, continuity, or weak signals.
5. Plays a role in electromagnetic induction experiments to observe induced current.
6. Essential in scientific research and laboratories for precise electrical measurements.
7. It is used in optical instruments, such as mirror galvanometers in laser systems.
8. Applied in medical devices like ECG and EEG machines to detect bioelectrical signals.
9. It is used in telecommunications for signal detection and monitoring.