What is the equivalent resistance of resistors $R_{1}$ and $R_{2}$ connected in parallel connection?

An electric iron consumes energy at a rate of $840\, W$ when heating is at the maximum rate and $360\, W$ when the heating is at the minimum. The voltage is $220\, V$. What are the current and the resistance in each case?

$(a)$ In the circuit shown, connect a nichrome wire of length $L$ between points $X$ and $Y$ and note the ammeter reading.
$(i)$ When this experiment is repeated by inserting another nichrome wire of the same thickness but twice the length $(2L)$, what changes are observed in the ammeter reading?
$(ii)$ State the changes that are observed in the ammeter reading if we double the area of cross-section without changing the length in the above experiment. Justify your answer in both cases.
$(b)$ "Potential difference between points $A$ and $B$ in an electric field is $1\, V$." Explain the statement.

How much current will an electric bulb of resistance $1100 \ \Omega$ draw from a $220 \ V$ source? If a heater of resistance $100 \ \Omega$ is connected to the same source instead of the bulb,calculate the current drawn by the heater.

$(a)$ What are the values of $mA$ and $\mu A$ in terms of Ampere $(A)$?
$(b)$ Draw the symbols of a battery and a rheostat.

$(a)$ What do the following symbols represent in a circuit? Write the name and one function of each.
$(b)$ Draw a schematic diagram of a circuit consisting of a battery of $12 \, V$,three resistors of $5 \, \Omega$,$10 \, \Omega$,and $20 \, \Omega$ connected in parallel,an ammeter to measure the total current through the circuit,and a voltmeter to measure the potential difference across the combination of resistors.
$(c)$ State any one advantage of connecting electrical devices in parallel with the mains instead of connecting them in series in a household circuit.