Answer:
(a) Ammeter is used to measure current. Its unit of current is ampere A. One ampere is defined as the current which will flow in a resistor of when 1 V potential difference is applied across it ends. (1)
(b) (i) Rheostat (ii) Closed key (1)
(c) (i) An electric circuit given relation is shown below
(ii) From the graph, when potential difference is 1.6 V and current is 0.6 A.
Therefore, value of ratio for all potential difference 0.8 V, 1.2 V and 1.6 V will be equal to 2.67 . (1)
We conclude that at the given temperature, the resistance of wire is constant and is equal to 2.67 . (1)
Or
In a household electric circuit, different appliances are connected in parallel to one another because
(i) Each appliance may be independently used.
(ii) Each appliance may get the required potential. (1 x 2)
Given,
P = 1.5 kW = 1500 W, V = 220 V
Current drawn (1)
The fuse wire will melt and disconnect the electrical heater from the mains since it can bear only 5A. But to run the heater, instead of 5A fuse, one should use a fuse with a slightly higher capacity to handle a current more than 6.82 A, thus a 10 A fuse is required. (2)
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