Class 12 Physics simulations · Current Electricity

Potentiometer: comparing EMFs

Slide the jockey along a 1 m wire until the galvanometer reads zero. The balancing length measures the cell’s EMF.

Open the simulation

What to notice

At balance no current flows through the cell, so its true EMF — not its terminal voltage — is measured.

Key relation

E = k l, k = E₀R_w / [(R_w + R_h) L]

Try this

Increase the rheostat resistance. Does the balance point move further along?

What you can change

• Driver cell E₀: 2 to 6 V
• Rheostat: 0 to 20 Ω
• Test cell EMF: 0.5 to 2 V
• Jockey position: 0 to 100 cm

More in Current Electricity

• Cells in series and parallel
• Ohm’s law circuit
• Electron drift in a wire
• A real cell under load
• Kirchhoff’s laws: two-loop circuit
• Resistance and temperature
• Series and parallel resistors
• Wheatstone bridge

See all Class 12 Physics simulations or every Physica simulation.