Electric Current
Electric current is the flow of electric charge (electrons) through a conductor. Symbol: I. Unit: Ampere (A).
I = Q / t (Current = Charge ÷ Time)
Voltage (Potential Difference)
Voltage is the energy per unit charge that drives current through a circuit. Symbol: V. Unit: Volt (V).
Resistance
Resistance is the opposition to the flow of electric current. Symbol: R. Unit: Ohm (Ω).
Ohm's Law
V = IR | Voltage = Current × Resistance
Example: A resistor has resistance 10 Ω and carries a current of 2 A. V = 2 × 10 = 20 V
Series and Parallel Circuits
| Feature | Series | Parallel |
|---|---|---|
| Current | Same throughout | Splits at junctions |
| Voltage | Splits across components | Same across each branch |
| Total Resistance | R_total = R₁+R₂+... (increases) | 1/R_total = 1/R₁+1/R₂ (decreases) |
| If one bulb breaks | All go out | Others stay on |
Electrical Power
P = IV | Power (W) = Current (A) × Voltage (V)
💡 In Nigeria, household electricity runs at 240 V (when available). Appliances are rated by power (watts). Energy used = Power × Time.