Electric cells
● We use electric cells to supply the energy needed for electrons to move around an electric
circuit.
● The electric cell system works to generate electricity.
A cell does not have moving parts to generate electricity. An electrical cell generates electricity from
chemical reactions.
CHEMICAL REACTION WITH A LEMON
A chemical reaction takes place inside the lemon which produces electricity. The copper and zinc nails
(metal strips) are the electrodes and the lemon juice acts as the electrolyte.
➔ Citrus fruits (like lemons) are acidic, which helps their juice to conduct electricity.
When electrodes are connected in a circuit, a chemical reaction takes place within the electrolyte in
the lemon, which causes the electrons to move in the external circuit.
➔ This will only occur when the cell is connected in the circuit.
Chemical reactions only take place when the battery is connected in a circuit.
➔ When you store a battery for a long time, it won’t go flat.
RESISTANCE
An electric current is the rate of a charge flow in a closed circuit. The electrons in an atom are
arranged in the outer space around the central nucleus.
Resistance slows down the flow of current in an electric circuit.
● In metals, the electrons are able to move freely within the metal.
➔ We say electrons in a metal are delocalised.
● Conducting wires in electrical circuits are made of metal. If we supply a source of energy in a
complete circuit, the electrons will move in the same general direction through the wire to
the positive terminal of the battery. This movement of electrons is the electric current.
● Electrical conductors have some resistance.
● We use electric cells to supply the energy needed for electrons to move around an electric
circuit.
● The electric cell system works to generate electricity.
A cell does not have moving parts to generate electricity. An electrical cell generates electricity from
chemical reactions.
CHEMICAL REACTION WITH A LEMON
A chemical reaction takes place inside the lemon which produces electricity. The copper and zinc nails
(metal strips) are the electrodes and the lemon juice acts as the electrolyte.
➔ Citrus fruits (like lemons) are acidic, which helps their juice to conduct electricity.
When electrodes are connected in a circuit, a chemical reaction takes place within the electrolyte in
the lemon, which causes the electrons to move in the external circuit.
➔ This will only occur when the cell is connected in the circuit.
Chemical reactions only take place when the battery is connected in a circuit.
➔ When you store a battery for a long time, it won’t go flat.
RESISTANCE
An electric current is the rate of a charge flow in a closed circuit. The electrons in an atom are
arranged in the outer space around the central nucleus.
Resistance slows down the flow of current in an electric circuit.
● In metals, the electrons are able to move freely within the metal.
➔ We say electrons in a metal are delocalised.
● Conducting wires in electrical circuits are made of metal. If we supply a source of energy in a
complete circuit, the electrons will move in the same general direction through the wire to
the positive terminal of the battery. This movement of electrons is the electric current.
● Electrical conductors have some resistance.
