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is immersed in 1 litre of water. The heater is connected to a voltage of 220 V. The initial water temperature is 
. After 4 minutes,the water is heated to 
. What is the efficiency of converting electricity into heat energy?
and it's heated by 2 K in one minute.
, its density is 
, and its specific heat capacity is 
.
and that of the second resistor is 
. The power dissipated by the second resistor is 2 W. What is the power dissipated by the first resistor?
.
is chosen. If the thickness of the wire is 0.8 mm, how long should the wire be?
, 
and 
, as shown. The cell provides power to the circuit and power is dissipated in the resistors.
and charge 
?
when a current of 
passes through it. The variable resistor is adjusted so that the power dissipated in X increases by 
. What is the new current in the circuit?
mains supply. What are possible values for the power of the kettle and the current in the kettle?
. In the circuit on the left, the power dissipated in the resistor is 
. What is the total power dissipated in the circuit on the right?
is connected across a cell of electromotive force (e.m.f.) 
and negligible internal resistance. Which single change to the circuit would lead to the largest increase in the power dissipated in the resistor.
and 
are connected in parallel with a battery of electromotive force (e.m.f.) 
and negligible internal resistance.
. What is the value of 
through a filament lamp varies with the potential difference 
across it?
. The power supply has an output power of 
and a terminal potential difference of 
. How much thermal energy is dissipated in the connecting wires in a time of 1.0 hour?
, as shown.
for a time of 
. During this time 
of energy is dissipated by the internal resistance. What is the energy supplied to the external resistor during the 
and its resistance is 
. The current in lamp Y is 
and its resistance is 
.
?
. When the potential difference (p.d.) across the resistor is 
, the current in the resistor is 
. The power dissipated in the resistor is 
. Work 
is done when charge 
flows through the resistor. What is not a valid relationship between these variables?
. After a time of 1.0 hour, the initial current of 
slowly decreases to zero, as shown.
. What does this mean?
of electrical energy to the whole circuit.
, which describes the power supplied to the heating coil in the kettle. The coil has a resistance of 
. What is the current in the coil?
at a potential difference (p.d.) of 
. The two wires between the supply and a kettle each have a resistance of 
, as shown.
