Electrical appliances at home are normally earthed so that?
the appliances are maintained at a lower p.d than the earth
both the a.c and d.c sources can be used
a person touching the appliances is safe from electric shock
the appliances are maintained at a higher p.d than the earth
Correct answer is C
Earthing is used to protect you from an electric shock. It does this by providing a path (a protective conductor) for a fault current to flow to earth. It also causes the protective device (either a circuit-breaker or fuse) to switch off the electric current to the circuit that has the fault.
1.00 x 1020
2.56 x 10-18
2.56 x -17
1.00 x 1017
Correct answer is D
Current (I) = q/t → q = i x t
= 16 x 10-3 x 1
= 1.6 x 10-2C
But 1.6 x 10-19C = I electronic charge
1 coulomb = 1 / (1.6x10-19)
∴ 1.6 x 10-2 coulombs = 1 / (1.6x10-19) x 1.6x10-2 / 1
= 1.0 x 10-2 x 1019
= 1.0 x 1017
The instrument used for securing a large number of similar charges by induction is called
electrophorus
capacitor
proof-plane
electroscope
Correct answer is A
No explanation has been provided for this answer.
9.6J
2.4J
12.0J
7.2J
Correct answer is B
Energy stored = Ivt = current x back e.m.f x time
= 2 x 3 x 0.4
= 2.4J
The energy stored in an inductor of inductance 5mH when a current of 6A flows through it is
9.0 x 10-3J
9.0 x 10-2J
1.4 x 10-2J
1.8 x 10-3J
Correct answer is B
Energy stored in a coil of inductance, L, and carry a current, I is given by
E = 1/2 L I2
= 1/2 x 5 x 10-3 x 6 x 6
= 9.0 x 10-2J