Physics 2nd unit Electrostatic Potential and Capacitance HS 2nd year

 

🔬 Experiment 1: Visualizing Equipotential Surfaces

Objective:
To demonstrate that electric field lines are perpendicular to equipotential surfaces.

Apparatus:

• Conductive paper

• Power supply (DC)

• Electrodes (point and line types)

• Voltmeter

• Probe (metal needle)

• Connecting wires

Procedure:

1. Place two electrodes on the conductive paper (e.g., a point and a line electrode).

2. Connect them to the power supply.

3. Use the probe and voltmeter to find points of equal potential.

4. Mark the equipotential points and connect them to form surfaces (lines).

5. Draw electric field lines as perpendiculars to these surfaces.

Observation:
Equipotential lines are always perpendicular to electric field lines.

Conclusion:
Confirms that no work is done when moving a charge along an equipotential surface.

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⚡ Experiment 2: Electric Potential Due to a Point Charge

Objective:
To verify the relation $V = \frac{1}{4\pi\epsilon_0} \cdot \frac{Q}{r}$

Apparatus:

• Point source (charged metal sphere)

• Electrometer or voltmeter

• Scale

• Variable distance measuring setup

• Insulated platform

Procedure:

1. Charge the sphere and place it on an insulated stand.

2. Measure potential at various distances using the voltmeter.

3. Record $V$ for different values of $r$.

4. Plot a graph of $V$ vs $\frac{1}{r}$.

Observation:
A straight line validates inverse relationship.

Conclusion:
Electric potential due to a point charge follows the inverse-distance law.

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🧲 Experiment 3: Behavior of a Dipole in an Electric Field

Objective:
To observe torque on a dipole placed in a uniform electric field.

Apparatus:

• Small bar magnet or pair of opposite charges on a stick

• Stand with pivot

• Electrostatic generator or parallel plate capacitor

• Protractor

Procedure:

1. Place the dipole in the field between the plates.

2. Observe and record the angle it makes with the field.

3. Release and allow it to align.

Observation:
The dipole rotates to align with the electric field.

Conclusion:
Torque acts on a dipole in an electric field, aligning it along the field lines.

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🧪 Experiment 4: Capacitance of a Parallel Plate Capacitor

Objective:
To measure the capacitance of a parallel plate capacitor using known charge and voltage.

Apparatus:

• Two parallel metal plates

• Micrometer screw gauge (to vary distance)

• DC power supply

• Electrometer or charge sensor

• Dielectric materials (optional)

Procedure:

1. Measure the area and separation of plates.

2. Charge the capacitor using power supply.

3. Measure the charge and voltage.

4. Calculate $C = \frac{Q}{V}$.

5. Repeat for different plate separations and dielectric insertions.

Observation:
Capacitance increases with area, decreases with distance, and increases with dielectric.

Conclusion:
Confirms theoretical relation:
$C = \frac{\varepsilon_0 A}{d} \quad \text{and} \quad C' = K \cdot C \text{ (with dielectric)}$