1) Current and Circuit symbols:

1. Basics of Current and Charge Flow

• Current: Flow of electrical charge (electrons).

• Condition: Only flows in a closed circuit with potential difference (p.d.).

• Unit of Current: Ampere (A).

2. Potential Difference and Resistance

• Potential Difference (Voltage): Drives the charge around the circuit.

  • Unit: Volt (V).

• Resistance: Opposes the flow of current.

  • Unit: Ohm (Ω).

3. Circuit Behaviour

• In a single, closed loop, the current is the same throughout.

• Formula: Q=I×tQ=I×t

  • Q = Charge (Coulombs, C)

  • I = Current (A)

  • t = Time (seconds, s)

4. Current and Resistance Relationship

• Higher Resistance = Lower Current (for a fixed p.d.).

• Example Calculation:

  • If a current of 2 A flows for 2.5 hours, charge Q=2×(2.5×3600)=18000Q=2×(2.5×3600)=18000 C.

Circuit Symbols: