Electric current and potential difference

Introduction to electricity

Think of electricity like water flowing in a pipe. Just as water flows from a high tank to a low tap, electricity flows from one point to another. In our homes, when NEPA or PHCN restores light, charges start moving through the wires to power our bulbs and fans.

Electric current

Electric current is simply the flow of electric charges, usually electrons, through a conductor like a copper wire. If the charges are not moving, there is no current. It is measured using an instrument called an ammeter, which must always be connected in series.

In simple terms, current tells us how many charges pass a point in one second.

The formula for current is I = Q / t, where I is current in Amperes (A), Q is charge in Coulombs (C), and t is time in seconds (s).

Potential difference

For water to flow, one end of the pipe must be higher than the other. In electricity, for current to flow, there must be a 'pressure' difference between two points. This pressure is what we call Potential Difference (P.D.) or Voltage.

Simply put, P.D. is the electrical 'push' that makes current move between two points.

We measure P.D. in Volts (V) using a voltmeter. A voltmeter is always connected in parallel across the two points we want to measure.

The formula is V = W / Q, where V is potential difference, W is work done or energy in Joules (J), and Q is the charge in Coulombs.

Worked example

If a charge of 30 Coulombs flows through a wire for 2 minutes, what is the current produced:

1. Write down what you know: Q = 30 C, t = 2 minutes.

2. Convert time to seconds: 2 minutes = 2 x 60 = 120 seconds.

3. Use the formula: I = Q / t.

4. Calculate: I = 30 / 120 = 0.25 A.

5. The current is 0.25 Amperes.