Download electricity and magnetism

ELECTRICITY
AND
MAGNETISM
CIRCUIT AND
COMPONENTS

BY: Tanisha Alexander
 5A
CIRCUIT DIAGRAMS
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Cell: supplies d.c. Dry cells may be rechargeable or non-rechargeable. Wet
cells are rechargeable.
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D.c supply
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a.c supply
CIRCUIT DIAGRAMS
Switch- opens and closes electric and electronic
circuits.
Fixed resistor- resistors control current flow in electric
circuits
CIRCUIT DIAGRAMS
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Variable Resistor- also called a rheostat and is used to maintain a
steady value of current.
Filament lamp- sometimes used as a current detector. Consists of an
evacuated glass envelope and a thin filament.
CIRCUIT DIAGRAMS
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Ammeter- a current measuring device placed in series with the
component.
Voltmeter- a device for measuring potential difference and is placed
in parallel with the component.
CIRCUIT DIAGRAMS
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Fuse- protects wires, parts of circuits or whole circuits from damage
by excessive currents. Fuses are placed in the live wire of a.c.
circuits.
Earth- this connection protects users of electrical equipment from
electrical shocks caused by stray currents.
CIRCUIT DIAGRAMS
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Junction- wires are actually connected
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Conductors crossing- wires cross but do not touch
CIRCUIT DIAGRAMS
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Semiconductor diode- allows electron flow in one direction only.
Used to change a.c to d.c i.e. in rectification.
Battery of cells- a series combination of identical cells
CELLS
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THE DRY CELL
The common dry cell has a zinc outer case which serves as the
negative terminal. A central carbon rod is the positive terminal.
Ammonium Chloride in the form of jelly is the electrolyte. The dry
cell also contains a mixture of powdered carbon and manganese
dioxide. The carbon improves conduction, the manganese dioxide
reduces polarization. Polarization is the process by which hydrogen
atoms build up around the positive terminal of the cell or battery.
Polarization reduces both the potential difference and the current
that the cell can provide.
THE PRIMARY CELL
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In a primary cell, the reactions cannot be reversed.

Primary cells cannot be recharged.

Example: A Dry Cell
THE SECONDARY CELL
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In secondary cells, the reactions can be reversed, therefore they can
be recharged again and again.
Example: The Lead-acid Battery
THE LEAD- ACID BATTERY:
The lead-acid battery has a negative plate made of soft lead. It
normally looks grey. The positive plat is made of lead dioxide which
is red and the electrolyte is sulphuric acid. When a battery is in use
or being discharged, both the negative and positive plates are
converted to lead sulphate.
DIFFERENCE BETWEEN A PRIMARY
CELL AND A SECONDARY CELL

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PRIMARY CELL
Primary cells are cheaper to
produce
Primary cells are easier to
install
Primary cells have higher
internal resistance, thus they
cannot supply large currents
without being damaged
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SECONDARY CELL
Secondary cells are more
expensive to produce
Secondary cells are harder to
install
Secondary cells have lower
internal resistance, thus they
can supply large currents
without getting damaged.
RECHARGING A LEAD-AID
BATTERY

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The following points should be noted carefully:
The positive end of the d.c. supply is joined to the positive end of
the battery.

Low charging currents should be used

he variable resistor is used to control the current.
CIRCUIT DIAGRAM TO SHOW HOW THE
LEAD-ACID BATTERY CAN BE
RECHARGED
 Circuit diagram:
QUIZ
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1) Draw the symbols for a fixed resistor, a battery, a voltmeter and a
fuse.
2) List and the describe the components of a zinc carbon dry cell
3) Distinguish between a primary cell and a secondary cell and give
an example of each.
4)Give three points that should be noted when recharging a leadacid battery.
5)Draw a circuit diagram to show how a lead-acid battery can be
recharged.
THANK YOU FOR
VIEWING.
Drawings were made by
Tanisha Alexander and not by a
website.