Science Answer the following question.

If the physical state of a conductor remains constant, the current (I) flowing through it is directly proportional to the potential difference (V) between its two ends.I α V
I = kV (k = constant of proportionality)

This is known as Ohm’s law.
We can obtain the SI unit of resistance from the above formula, Potential difference and current are measured in Volts and Amperes respectively. The unit o resistance is called Ohm. It is indicated by the symbol Ω.

The resistance of one Ohm : If one Ampere current flows through a conductor when one Volt potential difference is applied between its ends, then the resistance of the conductor is one Ohm.

• Electric switches and sockets should be fitted at a height at which small children cannot reach and put pins or nails inside. Plug wires should not be pulled while removing a plug from its socket.
• Before cleaning an electrical appliance it should be switched off and its plug removed from the socket.
• One’s hands should be dry while handling an electrical appliance, and, as far as possible, one should use footwear with rubber soles.
• As rubber is an insulator, it prevents the current from flowing through our body, thereby protecting it.
• If a person gets an electric shock, you should not touch that person. You should switch off the main switch or remove the plug from the socket if possible.
• 1f not, then you should use a wooden pole to push the person away from the electric wire.

• Fuse wire is used to protect domestic appliances.
• It is made of a mixture of substances and has a specific melting point.
• It is connected in series to the electric appliances. If for some reason, the current in the circuit increases excessively, the fuse wire gets heated and melts. The circuit gets broken and the flow of current stops, thus protecting the appliance.
• This wire is fitted in a groove in a body of porcelain-like non-conducting material. For domestic use, fuse wires with upper limits of 1A, 2A, 3A, 4A, 5A, and lO Aareused.

(i) At a given temperature, the resistance (R) of a conductor depends on its length (L), area of cross-section (A) and the material it is made of. If the resistance of a conductor is R, then

(ii) p is the constant of proportionality and is called the resistivity of the material.
(iii) The unit of resistivity in SI units is Ohm metre (Ω m).
(iv) Resistivity is a specific property of a material and different materials have different resistivity. ’