Electricity

Two resistors of 4Ω and 6Ω are connected in parallel. This combination is connected in series with a 3Ω resistor. Calculate the equivalent resistance of the circuit. [CBSE 2025]

An electric bulb is rated 220V, 100W. Calculate: (a) its resistance (b) current flowing through it when connected to 220V supply. [CBSE 2024]

State Ohm's law. Draw a circuit diagram to verify it experimentally. Draw the V-I graph for a conductor obeying Ohm's law. [CBSE 2023]

An electric iron consumes energy at the rate of 840W when the current of 7A flows through it. Calculate the resistance and voltage of the electric iron. [CBSE 2022]

How much current will an electric heater of 1000W draw from a 250V supply line? What should be the resistance of the heater? [CBSE 2021]

V = IR V = Potential difference (Volts) I = Current (Amperes) R = Resistance (Ohms)

P = VI = I²R = V²/R P = Power (Watts)

E = P × t = VIt E = Energy (Joules or kWh) 1 kWh = 3.6 × 10⁶ J = 1 Unit

R_s = R₁ + R₂ + R₃ + ... Current same, voltage divides

1/R_p = 1/R₁ + 1/R₂ + 1/R₃ + ... Voltage same, current divides

H = I²Rt = VIt = V²t/R H = Heat produced (Joules)

Consider drift velocity v_d = eEτ/m Current I = neAv_d Substituting and simplifying: V = IR, where R = mL/(ne²Aτ)

In series: Same current I flows through all V = V₁ + V₂ + V₃ IR = IR₁ + IR₂ + IR₃ R = R₁ + R₂ + R₃

In parallel: Same voltage V across all I = I₁ + I₂ + I₃ V/R = V/R₁ + V/R₂ + V/R₃ 1/R = 1/R₁ + 1/R₂ + 1/R₃