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Electrical Voltage

Electrical voltage is also called as electric potential and is defined as the electrical potential difference between two electrical poles of the battery during the flow of electric current.

Let us consider the example of a battery; battery consists of two electrical poles – positive and negative electrical pole. Chemical process taking places in battery results into chemical force or non electrical force. Due to chemical force, positive charges move towards positive poles and negative charges move towards negative pole and get accumulated there. The process of accumulating charges at respective poles produces electrical potential difference between two poles and is increases gradually. Once the electrical potential difference reaches the maximum and there is no further accumulation of charges at respective poles, at this time the electrical potential difference and chemical force becomes equal. The electrical potential difference at this point is called emf – electromotive force of the battery.

The unit of emf is joule/coulomb = volt. The name is given in the memory of scientist Volta.

Suppose we attach battery with a conducting wire, then the electric field is generated. Due to electric field, positive charges flow towards negative force and constitute an electric current. Hence the potential difference between two electrical poles is varying when the electric current is flowing. This electrical potential difference between two poles of the battery during the flow of current is called terminal voltage or electrical voltage or electrical potential.

The relationship between voltage and emf is given as
V = E – I
× r
Where we have
V= Voltage
E = electromotive force
I = current
r = internal resistance

The instrument used to measure the electric potential or electric voltage between any two points is called Voltmeter and is connected parallel to the two concerned points.

Calculation Examples

Example-1: The internal resistance of a 12V battery is 0.17 ohm when current flows form the battery is 0.1 x 104 mA; calculate the terminal voltage of the battery.

Reason:

Here we have:
E = 12V
r = 0.17 ohm
I = 0.1
× 104 mA = 1000 mA = 1 A

V = E – Ir
= 12 – (1
× 0.17)
= 11.8 V

Example-2: Why did not the positive charges move from positive pole to the negative pole of the battery prior to connecting with the conducting wire?

a)  Positive charges faces opposition form internal resistance of the battery
b)  Positive charges faces opposition from the non-electrical force
c)  Energy of the positive charges becomes zero as soon as it reaches to positive charge
d)  None of above

Reason: The positive charges faces opposition from the non-electrical force before connecting the battery with the conducting wire.

Example-3: The instrument used for measuring the electric voltage is……………

a)  Ammeter
b)  Wheatstone bridge
c)  Galvanometer
d)  Voltmeter

Reason: the instrument used for measuring the electric voltage is voltmeter.

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