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Step 1: List the known quantities
- Resistance, R = 10 Ω
- Current, I = 0.3 A
Step 2: Write the equation relating resistance, potential difference and current
V = IR
Step 3: Substitute in the values
V = 0.3 × 10 = 3 V
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High resistance means there is lower current and vice versa
Resistance can be tricky to grasp conceptually because the definition 'opposition to current' is a bit difficult to pin down.
From the point of view of a tiny electron flowing through a wire, the wire is this huge structure of metal ions arranged in a lattice. There are millions of other electrons flowing through the wire too. Every time an electron hits the lattice, the electron transfers some of its energy to the lattice. The electron loses energy and slows down a bit, and the lattice gains energy and vibrates more and more with each collision. The more it shakes, the more the electrons collide with it.
The wire heats up due to the collisions of electrons with the lattice of the metal ions in the wire. The hotter it gets, the more it vibrates, the more collisions there are. The more collisions there are, the hotter it gets... and on and on and on.
Voltage, current, resistance formula triangle
Calculate the potential difference through a resistor of resistance 10 Ω if there is a current of 0.3 A through it.
Step 1: List the known quantities
Step 2: Write the equation relating resistance, potential difference and current
V = IR
Step 3: Substitute in the values
V = 0.3 × 10 = 3 V
Remember that 'voltage' and 'potential difference' are the same, either wording will be accepted in your exam answers
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