Keshu

1. What is an Electric Circuit?

An electric circuit is a closed path that allows electric current to flow.

Basic parts of a circuit:

• Source → cell or battery (provides energy)

• Conducting path → wires

• Load → bulb, resistor, motor (uses energy)

• Switch (optional) → opens or closes the circuit

If the circuit is open → no currentIf the circuit is closed → current flows

2. Electric Current (Amps)

Electric current is the rate of flow of electric charge.

• Measured in Amperes (A)

• Formula:

Q

I = --

t

(Current = charge / time)

Important idea:

• Current flows only when there is a voltage difference

• Current depends on:

  • Voltage

  • Resistance of the circuit

3. Voltage (Potential Difference)

Voltage is the energy given to each charge by the source.

• Measured in Volts (V)

• Think of voltage as push or pressure that moves electrons

Water analogy:

• Voltage = water pressure

• Current = flow rate of water

• Resistance = pipe thickness

More voltage → stronger push → more current (if resistance is same)

4. Cell and Its Voltage

A cell converts chemical energy → electrical energy.

• A single dry cell ≈ 1.5 V

• This means each coulomb of charge gets 1.5 joules of energy

One cell provides:

• Fixed voltage (e.g., 1.5 V)

• Limited current (depends on internal resistance)

5. More Cells → What Happens?

(A) Cells in Series → More Voltage

When cells are connected end to end:

+ − + − + −

Total Voltage = Sum of individual voltages

Example:

• 1 cell = 1.5 V

• 2 cells in series = 3 V

• 4 cells in series = 6 V

Effects:

• Voltage increases

• Current increases (if resistance stays same)

• Bulb glows brighter

More Voltage vs More Current (Important Difference)

More Voltage:

• Higher energy per charge

• Faster electron movement

• Can damage devices if too high

More Current:

• More charge flowing

• Causes heating

• Thick wires needed for high current

Key point: