An electric iron of resistance $20\, \Omega$ takes a current of $5\, A$. Calculate the heat developed in $30\, s$.

An electric lamp of $100 \,\Omega$,a toaster of resistance $50 \,\Omega$,and a water filter of resistance $500 \,\Omega$ are connected in parallel to a $220 \,V$ source. What is the resistance of an electric iron connected to the same source that takes as much current as all three appliances,and what is the current through it?

$A$ hot plate of an electric oven connected to a $220\, V$ line has two resistance coils $A$ and $B$,each of $24\,\Omega$ resistance,which may be used separately,in series,or in parallel. What are the currents in the three cases?

Draw a schematic diagram of a circuit consisting of a battery of three cells of $2\, V$ each,a $5\,\Omega$ resistor,an $8\,\Omega$ resistor,and a $12\,\Omega$ resistor,and a plug key,all connected in series. Include an ammeter to measure the current through the resistors and a voltmeter to measure the potential difference across the $12\,\Omega$ resistor. What would be the readings in the ammeter and the voltmeter?

Which of the following terms does not represent electrical power in a circuit?

When a $12\, V$ battery is connected across an unknown resistor,there is a current of $2.5\, mA$ in the circuit. Find the value of the resistance of the resistor.