Page 111 - Physics 10_Float

CURRENT ELECTRICITY

14.14 SAFE USE OF ELECTRICITY IN HOMES Identifying Circuit
Components
In order to protect persons, devices and property from the
Wires crossed
hazards of electricity there is a need of extensive safety not joined
measures in household electricity. Take much care to use
Wires crossed
fuses and circuit breakers in an electric circuit as safety at a junction
devices. They prevent circuit overloads that can occur when Variable
nesistor
too many appliances are turned ON at the same time or when
a short circuit occurs in one appliance. Fixed resistor
Fuse Diode
A fuse is a safety device that is connected in series with the Earth or
ground
livewire in the circuit to protect the equipments when excess
current flows. It is short and thin piece of metal wire that Battery or
DC supply
melts when large current passes through it. If a large, unsafe
current passes through the circuit, the fuse melts and breaks Capacitor
the circuit before the wires become very hot and cause fire.
Time-varying or
Fuses are normally rated as 5 A, 10 A, 13 A,30 A, etc. Different AC supply
types of fuses are shown in Fig.14.18.
Ammeter
Following safety measures should be taken while using fuses
Voltmeter
in household electrical circuits:
(i) Fuses to be used should have slightly more rating than the Ohmmeter
current which the electrical appliance will draw under Thermister or
temperature-
normal conditions. For example, for a lightning circuit choose dependent resistor
a 5 A fuse as the current drawn by each lamp is very small
Switch
(about 0.4 A for a 100 W lamp). In such circuit, 10 lamps of
100 W can be safely used as the total current drawn is only 4 A Lamp/bulb
which can be calculated using the formula P = VI.

Fig. 14 .18: Different types of fuses
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