Download Electricity in the Home

Focus 3: Series and parallel circuits serve different purposes
in households
and
Focus 6: Safety devices are important in household circuits.
Series and Parallel Circuits
 identify the difference between series and parallel
circuits
Compare parallel and series circuits in terms of voltage
across components and current through them.
Series Connection
Circuit diagram
Potential Difference (V)
Current (I)
Resistance (R)
Parallel Connection
Ammeters and
Voltmeters
 Ammeters are used to measure the current in a circuit.
 They are placed in series to allow the same current to flow
through them as flows through the components in the circuit.
They have a low resistance to ensure that they don’t block the
flow of current.
 Voltmeters are used to measure the difference in energy
between two points in a circuit (the electrical potential
difference or voltage)
 They are placed in parallel with the part of the circuit you are
trying to measure so as to be able to measure the change in
potential from one side to the other. They have a high
resistance so little current is diverted through the voltmeter
Circuits in the House
From http://www.nointrigue.com/docs/notes/physics/phys_y11circuits.pdf
 Why are there different circuits for lighting, heating and other
appliances in a house?
When a current passes through a conductor, heat is generated.
The amount of heat generated increases as the current through
the conductor increases. Each piece of household wiring is
designed to carry a certain maximum current without
overheating. However, different devices have different power
requirements and have different current requirements because
voltage is the same in all domestic supplies. So, for example, the
circuit connecting devices requiring high currents (e.g. ovens
and hot-water systems), it would be necessary to use thicker
wiring to avoid overheating and circuit breakers that are
designed for the high current. Thus, different circuits are needed
for lighting, heating and other appliances because the current
requirement is different for each one.
 Compare the structure of a household circuit for different
purposes.
In general, there are a number of circuits each designed to carry a
certain maximum current, each with a fuse in the active wire. There are
separate circuits for light outlets, power outlets, the stove and the hotwater system. The outlets in each circuit are connected in parallel, so
that each appliance will have 240 V across it. There is a switch in series
with each outlet, enabling each appliance to be switched on and off
independently of the other appliances; this switch is on the active side
of the appliance because if the switch were on the neutral side, the
appliance could cause an electric shock even if it were switched off.
Furthermore, some domestic appliances, such as pottery kilns and
large air conditioners, use three-phase alternating current. Three-phase
AC is supplied using three active wires, each one-third of a cycle out of
phase with the other two, and one neutral wire. It can supply a more
consistent power to a device because current continues to be supplied
to the other two phases when the third is zero, resulting in a more
consistent flow of current and a corresponding increase in power to the
device.
Electric Shock
 discuss the dangers of an electric shock from both a
240 volt AC mains supply and various DC voltages,
from appliances, on the muscles of the body
Safety Devices
 describe the functions of circuit breakers, fuses,
earthing, double insulation and other safety devices in
the home