Page 5 - 10-phy-14 Current Electricity

14. Current Electricity eLearn.Punjab
For your information
Example 14.1: If 0.5 C charge passes through a wire in 10 s, then
what will be the value of current flowing through the wire?

Solution: Given that, Q = 0.5 C, t = 10 s, therefore by using
I = Q/t = 0.5 C/10 s=0.05 A= 50 mA

Conventional Current

Before the idea of free electrons which constitute current in A battery raises electric charge back
up to higher voltage(energy) just like
Physics insight metals, it was thought that a pump which pushes water back up
current in conductors flows to high energy so it can flow and do
work again.
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 charge in a circuit is like
the flow of water in a pipe except
that a return wire is needed in order
to have a complete conducting path.

The flow of current continues as long as there
is a potential difference.
Conventional current is defined as:

Current flowing from positive to Fig. 14.2: Current flows in a conductor when it is connected to a
negative terminal of a battery battery.

due to the flow of positive
charges is called conventional

current.

Conventional current produces the same effect as the
current flowing from negative terminal to the positive terminal due to the flow of negative charges.

5 V: 1.1