Current Electricity Test - 14

Kirchhoff’s loop rule is based on the principle of conservation of energy. Since work done in transporting a charge in a closed loop is zero. The algebraic sum ( since potential differences can be both positive and negative) of potential differences around any closed loop is always zero.

Potentiometer is a long wire of uniform cross section made of manganin.It is actually a wire with high resistivity (ρ) with uniform cross-sectional area A. Thus, throughout the wire, it has uniform resistance.

Unit of electric current assigned by institute of standards is Ampere. 1 ampere is the constant current that will produce an attractive force of 2 × 10⁻⁷ newton per metre of length between two straight, parallel conductors of infinite length and negligible circular cross section placed one metre apart in a vacuum.

Power is the rate of doing work per unit time. It is the amount of energy consumed per unit time. In the SI system unit of power is Joules per second which is also called Watt in honour of James Watt, the eighteenth-century developer of steam engine.

Ammeter is a device used to measure current. Since it has to allow the complete current flowing in the circuit through it, it has to be connected in series. For this reason, ammeters have very low values of resistances so that they do not add to the value of resistance connected in the circuit.

If a charge moves around a closed loop in a circuit, it must gain as much energy as it loses.Hence, the gain in electrical energy by the charge = corresponding losses in energy through resistances.

Potential gradient = V/I
If internal resistance of a battery is negligible then it does not affect equivalent resistance of potentiometer so potential gradient of potentiometer remains unchanged.