$A$ cell,a resistor,a key and an ammeter are arranged as shown in the circuit diagrams of the figure. The current recorded in the ammeter will be

$(a)$ $A$ Nichrome wire of length $L$ and radius $r$ has a resistance of $10 \, \Omega$. How would the resistance of the wire change when:
$(i)$ only the length of the wire is doubled?
$(ii)$ only the diameter of the wire is doubled? Justify your answer.
$(b)$ Why are the elements of electrical heating devices made up of alloys?

You are given three resistors of $10\, \Omega, 10\, \Omega, 20\, \Omega$,a battery of emf $2.5\, V$,a key,an ammeter,and a voltmeter. Draw a circuit diagram showing the correct connections of the given components such that the voltmeter gives a reading of $2.0\, V$.

Find the resistance of a bulb rated as $100 \, W - 250 \, V$.

$(a)$ What is an electric circuit?
$(b)$ Calculate the number of electrons that flow per second to constitute a current of one ampere. The charge on an electron is $1.6 \times 10^{-19} \ C$.
$(c)$ Draw an electric circuit for studying Ohm's law. Label the circuit components used to measure electric current and potential difference.

$1 \; kWh = \ldots \ldots \; \text{joules}$