Electricity

The devices which deliver electricity are called the 'sources'and lamps, electric engines, etc. which consume electricity are called 'loads'. Switches are used to switch the loads on and off whenever necessary. Hence, the source, the load, and the switch are connected together to form electrical circuits.

The circuit is called 'closed' when the current flows in the circuit, and when the current does not flow, it is called an 'open circuit'. The switch or key helps to make or break the circuit, i.e. switches on or switches off the current.

Components of An Electric Circuit

Sl.No.	Components	Symbols
01	An electric cell
02	A battery or a combination of cells
03	Plug key or switch (open)
04	Plug key or switch (closed)
05	A wire joint
06	Wires crossing without joining
07	Electric bulb
08	A resistor or resistance R
09	Variable resistance or rheostat
10	Ammeter
11	Voltmeter

Series and Parallel Circuits

If the components of a circuit are connected in a single loop, so that the same current flows through all the loads then the connection is called 'series' circuit.

But, if each of the components has a separate connection with a battery, then the circuit is said to be in parallel. The potential difference across the elements remain same.

Measuring Devices

A voltmeter is a device used to measure 'potential difference' and an ammeter is a device used to measure 'current'. Ammeters are connected 'in series' to the components through which the current to be measured flows. Voltmeters are connected in parallel to the components across which the potential difference is to be measured.