Question

Find the current in an element when the charge entering the element is q(t) = 10 e^-t C.
1. 10 e^t A
2. -10e^-t A
3. 10 A
4. -10 A

Answer 1

Correct Answer - Option 2 : -10e^-t A

Concept:

Electric current is expressed by the amount of charge flowing through a particular area in unit time. In other words, it is the rate of flow of electric charges.

In circuits using metallic wires, electrons constitute the flow of charges. However, electrons were not known at the time when the phenomenon of electricity was first observed. So, electric current was considered to be the flow of positive charges and the direction of flow of positive charges was taken to be the direction of electric current.

Conventionally, in an electric circuit, the direction of electric current is taken as opposite to the direction of the flow of electrons, which are negative charges.

When a charge is transferred from one point in the circuit to another point, it constitutes what is known as electric current.

Mathematically \(i = \frac{{dq}}{{dt}}\)

Calculation:

Given that, q(t) = 10 e-t C

Current \(i = \frac{{dq}}{{dt}} = - 10{e^{ - t}}A\)