Page 93 - Physics 10_Float

CURRENT ELECTRICITY

Conventional Current
Before the idea of free electrons which constitute current in
metals, it was thought that current in conductors flows due to
the motion of positive charges. Therefore, this convention is
still in use. We can understand the concept of conventional
current from the following analogies.
We know that when the ends of heated copper wire are at
different temperatures, heat energy flows from the end at
higher temperature to the end at lower temperature. The
flow stops when both ends reach the same temperature.
Water in a pipe also flows from higher level to the lower level.
Similarly, when a conductor is connected to a battery, it
pushes charges to flow current from higher potential to the
lower potential (Fig. 14.2). The flow of current continues as
long as there is a potential difference.
Current direction
V

Physics insight
Flow of free electrons

K + V - 1 litre s -1
Fig. 14.2: Current flows in a conductor when it is connected to a battery Pump
Conventional current is defined as:
Current flowing from positive to negative terminal of a battery
due to the flow of positive charges is called conventional current
- +
Conventional current produces the same effect as the -1
current flowing from negative terminal to the positive 1 C = 1 As
terminal due to the flow of negative charges. The flow of charge in a circuit is
like the flow of water in a pipe
The Measurement of Current except that a return wire is
How can we come to know that current has been established needed in order to have a
complete conducting path.
in the conductor? For this purpose, we use different electrical
instruments which detect the current in the circuit.
Galvanometer and ammeter are some common examples of
current measuring instruments.

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