The heating element of an electric kettle has a resistance of 30.0 Ω.
The kettle is connected to an a.c. power supply of root means square voltage 230 V.
The peak value of the current is:
15.2 A.
10.8 A.
7.7 A.
5.4 A.
The set up in the figure is used to study the relationship between current (I) and potential difference (V) for a wire X.
If the material X is a copper wire, the relationship between V and I when the switch is closed at constant temperature is:
Coulomb’s law.
Lenz’s law.
Hooke’s law.
Ohm’s law.
The value of X for which the galvanometer in the figure shows a null deflection is:
4.5 Ω.
8Ω.
1Ω.
4Ω.
The rheostat Y is used to:
Vary the resistance of the wire.
Vary electromotive force.
Vary the current in the circuit.
Keep the temperature constant.
The ammeter is connected as shown because it has:
Very low resistance and so alters the current flowing through it.
Very high resistance and so allows high current to flow through it.
Very low resistance and so does not alter the current flowing through it.
A very high resistance and so allows little current to flow through it.
