Electrical resistance changes current — Physical education, 11–13 years
Resistance is how strongly a component opposes electric current. It helps explain why wires warm up and how devices control the current they use.
A narrow path resists current
Electric current can pass through a component, but some components make that passage harder than others. This opposition is electrical resistance, measured in ohms. A larger resistance usually means less current for the same push from a battery, while a smaller resistance lets more current pass.
Why control the current?
Early electrical experiments faced a problem: a source could send too much current through a thin wire, making it hot or damaging equipment. Resistance gave people a way to limit and control that flow. They learned that the material, length and thickness of a conductor affect how strongly it resists current.
Calculating current
A 6 V battery is connected to a resistor of 3 ohms. The rule is current = voltage ÷ resistance. Step 1: write 6 V ÷ 3 ohms. Step 2: calculate 2 A. So the current is 2 amperes. If the resistor were 6 ohms instead, the same battery would give 1 A, because the harder path halves the current.
Resistance is not the same as a break
A reasonable mistake is to think that any resistance stops current completely. In fact, every real conductor has some resistance, and current can still pass through a component with a large resistance. An open switch is different: the path is broken, so there is no continuous route for current through that branch.
Heaters, dimmers and safety
A toaster and an electric heater use a wire designed to have enough resistance to become hot when current passes. A dimmer or sensor changes resistance so a lamp’s current can be controlled. Fuses and protective components also use resistance and heating effects to help stop dangerous currents before wires overheat.
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