Q2 of 72 Page 12

Define the unit of current.

The SI unit of electric current is Ampere, commonly denoted by letter A. 1 Ampere is defined as - When an amount of charge equivalent to 1 coulomb flows through a cross-section of a conductor in 1 second.

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44 Calculate the resistance of one metre of copper wire that has a cross–sectional area of about 2 x 10-2 cm2 (using the value of resistivity of copper to be 1.2 × 10-8 ohm m) Compare the value of this resistance with that of a flashlight bulb, which has a power rating of 1 W and operates at 3 V. What does this comparison tell you ? 1

Calculate the work done in moving a charge of 5 coulombs from a point at 20 to another at 30 V.

 3

What is electric potential?

 4

Name a device that helps to maintain a potential difference across a conductor.