At constant temperature, V ∝ I, i.e., V = IR. The ratio V/I = R (resistance) is constant for an ohmic conductor.

How does temperature affect resistance?

For metals, resistance increases with temperature: R_T = R₀(1 + αT). For semiconductors, resistance decreases with temperature.

What is the condition for a balanced Wheatstone bridge?

P/Q = R/S. When this condition is satisfied, no current flows through the galvanometer, so it can be used to find an unknown resistance precisely.

Ohm's Law and Resistance

Current Electricity • Class 11 Physics • NCERT • CBSE

Ohm's Law: V = IR. Resistance R = ρl/A. Series: R = R₁ + R₂. Parallel: 1/R = 1/R₁ + 1/R₂. Power P = VI = I²R = V²/R. Kirchhoff's Current Law: ΣI = 0 at junction. Kirchhoff's Voltage Law: ΣV = 0 in loop.

Key Formulas

V = IR (Ohm's Law)
R = ρl/A (resistance formula)
Series: R_total = R₁ + R₂ + ...
Parallel: 1/R = 1/R₁ + 1/R₂ + ...
P = VI = I²R = V²/R
Wheatstone bridge: P/Q = R/S

Frequently Asked Questions

State Ohm's Law.: At constant temperature, V ∝ I, i.e., V = IR. The ratio V/I = R (resistance) is constant for an ohmic conductor.
How does temperature affect resistance?: For metals, resistance increases with temperature: R_T = R₀(1 + αT). For semiconductors, resistance decreases with temperature.
What is the condition for a balanced Wheatstone bridge?: P/Q = R/S. When this condition is satisfied, no current flows through the galvanometer, so it can be used to find an unknown resistance precisely.

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