The potential difference between the terminals of an electric heater is $60\, V$ when it draws a current of $4\, A$ from the source. What current will the heater draw,if the potential difference is increased to $120\, V$ (in $, A$)?

Define resistance of a conductor. State the factors on which resistance of a conductor depends. Name the device which is often used to change the resistance without changing the voltage source in an electric circuit.
Calculate the resistance of $50 \, m$ length of wire of cross-sectional area $0.01 \, mm^2$ and of resistivity $5 \times 10^{-8} \, \Omega \, m$.

What are the factors on which the resistivity of a material depends?

Define resistivity of a material.

Study the $V - I$ graph for a resistor as shown in the figure and prepare a table showing the values of $I$ (in amperes) corresponding to four different values of $V$ (in volts). Find the value of current $I$ (amperes) for $V=10$ volts. How can we determine the resistance of the resistor from this graph?

Explain the term resistance. Give its $SI$ unit of measurement.