Chapter : 9 : Current and Voltage in a Circuit

-Shakil Raiman

Overview of the Chapter

Conductor Insulator Current Measuring Current Voltage Measuring Voltage

9.1: Conductors, Insulators and Electric Current:

An electric current is a flow of charge Electrons carry the charge Metals are good conductors as more

free electrons are present and electrons can move easily.

Electrons cannot move easily in insulators.

9.2: Electrons flow:

Some electron in a metal will flow when a voltage is applied.

9.3: Electric Current:

The rate of flow of charge is called an electric current.

Current = Charge / Time I = Q/t Unit: Ampere (A) It is measured by Ammeter. Ammeter has very low resistance. It is connected in series in a circuit.

9.4: Electric Charge:

Charge = Current × time Unit: Coulomb (C)

9.5: Voltage (Potential difference): Voltage is work done per unit charge

to transfer the charge across any point in a circuit.

Unit: Volt (V) It is measured by Voltmeter Voltmeter has high resistance It is connected in parallel to a device.

9.6: Electric Circuit: A circuit have power supply

(cell/battery), switch, any device and connecting wires.

Switch closed = ON, switch open = OFF

9.7: Circuit Symbols:

9.8: Series Circuit: A circuit with single loop where

current can flow in only one path is called series circuit.

The following picture shows the series circuit:

9.8.1: Advantages and Disadvantages of Series Circuit: Advantages:

Less wire is needed. Single switch can operate all devices.

Disadvantages: If one bulb breaks all other bulb will go off. As voltage is shared more the bulb added more the

dimmer they all become. Examples:

Decorative lights.

9.9: Parallel Circuit: A circuit with multiple loop where current

can flow in more than one path is called parallel circuit.

The following picture shows the series circuit:

9.9.1: Advantages and Disadvantages of Parallel Circuit: Advantages:

Each device can be operated individually. If one bulb breaks other works normally. All device can work with full power or all bulb can

work with full brightness. Disadvantages:

More wire is needed. Example:

Household connections.

9.10: Problems:

The end

THANK YOU ALL