10.
10. Consider the following assertion (a)
and the reason (r). Select the correct
alternative :
Assertion (a) : When high voltage
power is supplied through a domestic
wiring, immediately the running
television (ON condition) will burn out.
Reason (r) : DP switch is fitted in
domestic wiring to cut - off the power
supply automatically when high voltage
is supplied.
AS ’
“a' is true and 'r' is the correct
explanation to 'a'.
B) “a' is true and 'r' is the wrong
explanation to “a'.
C) “a' is false and 'r' is true,
D) Both 'a' and 'r' are false.
Answers
Answer:
A burnout, in electrical terms, is a drop in voltage across an electricity supply system. It can be spontaneous (unintentional) caused by disturbances in the grid, or intentionally caused during emergencies when the load needs to be reduced in order to prevent blackouts. The lower voltage causes lights to dim, leading to the name “burn out”.
Spontaneous burnouts usually cause voltage to drop for only a short period, while the intentional ones can have effects lasting anywhere from a few minutes to a few hours.
Effects of a Burnout
A burnout can prevent some electrical devices from getting harmed by power loads, but others can actually get damaged severely. Here are some facts that you should be aware of:
Power consumption is exponentially linked with voltage, so even small voltage drops can reduce heat output substantially. This can be observed in incandescent bulbs which become dimmer as voltage drops. The lower voltage during a burnout can, in this manner, protect devices from overheating.
In devices like some commutated electric motors, the drop in voltage lowers the back-EMF. This can increase the current drawn by the motor and create more heat.
Induction motors also heat up when they are operated on lower voltage and motors with insufficient cooling can eventually get damaged by overheating.
Electrical circuits with unregulated direct current supply continue feeding low voltage to all the connected appliances, increasing the chances of burnout. Regulated circuits protect appliances by constantly supplying the appropriate output voltage.
In case the burnout is severe, the voltage drop is higher than drop-out limit and the output voltage reduces. This creates a lot of ripple in electricity output.
Higher current draw to boost voltage produces more heat in the power supply and can eventually lead to total malfunction.
How to Avoid Electrical Burnout
There are a number of things you can do to avoid damage to your appliances from electrical burnout. Apart from grid-linked burnouts, voltage fluctuations can also occur from problems in the building’s basic electrical wiring. One of the first steps is to look at the electrical wiring diagram if you have it.