Contents
Key Stage 2
Meaning
Electrical Current is the amount of electricity flowing through a wire.
About Electrical Current
- The bigger the electrical current the brighter a bulb and the louder a buzzer.
- If an electrical current goes through an animal it is called an electrical shock.
Key Stage 3
Meaning
An electrical current is a flow of charge.
About Electrical Current
- Current is measured using an Ammeter.
- The units of current are amperes, which are also called amps (A).
- A current in a wire is a flow of electrons which are negatively charged particles.
- Conventional Current flows from positive to negative. This is because electricity was discovered before scientists knew about electrons.
- In a salt solution current is the flow of both positive and negative ions.
Key Stage 4
Meaning
Electrical current is the rate of flow of charge.
About Electrical Current
- Current is measured using an Ammeter.
- The SI Units of current are amperes, which are also called amps (A).
- A current in a wire is a flow of electrons which are negatively charged particles.
- Conventional Current flows from positive to negative. This is because electricity was discovered before scientists knew about electrons.
- In a salt solution current is the flow of both positive and negative ions.
- In a series circuit the current is the same everywhere in the circuit.
- In a parallel circuit the current splits at a junction.
Equation
Current = (Charge)/(time)
\(I=\frac{Q}{t}\)
Where\[I\] = The electrical current
\(Q\) = The amount of charge flowing past a point.
\(t\) = The time taken for the charge to flow.
- This can give the definition "Current (I) is the (=) amount of charge flowing past a point (Q) per (÷) unit time (t).
Example Calculations
A charge of 15 Coulombs passes through a point in a circuit ever 0.5 seconds. Calculate the current flowing past this point correct to two significant figures. | A capacitor stores a charge of 10C. It discharges in 12ms. Calculate the current flowing out of the capacitor correct to two significant figures. |
1. State the known quantities
Q = 15C t = 0.5s |
1. State the known quantities
Q = 10C t = 12ms = 12x10-3s |
2. Substitute the numbers into the equation and solve.
\(I=\frac{Q}{t}\) \(I=\frac{15}{0.5}\) \(I=30A\) |
2. Substitute the numbers into the equation and solve.
\(I=\frac{Q}{t}\) \(I=\frac{10}{12 \times 10^{-3}}\) \(I=833.3A\) \(I\approx830A\) |