Examiner's Expectation: 2.16 Students will be assessed during examination on their ability to understand that current is the rate of flow of charge

Examiner's Expectation: 2.17 Students will be assessed during examination on their ability to recall and use the relationship between charge, current and time:

charge = current × time

Q = I × t

We know that objects can develop charges (static charges through friction) and that these charges can move from one object to another and be distributed over a conductor. When electric charges move from one place to another, we say they constitute an electric current.

In metals, these moving charges are electrons, which have a negative charge.

Following cylinder shows the flow of negative charges in a conductor

Then the electric current "I" through the wire is

Current (I) = Charge (Q) / Time (t)

where, the unit of Charge is "Coulomb" and unit of time is "second". Therefore, unit of Current, which is Amperes (A) would be 1 A = 1 C / S

According to above equation, current is defined as flow of charges per second. Therefore, current can be increased by increasing the number of charges or increasing their speed (reducing time of flow.)

Try the following questions

Question#1

Question#2