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Power, current and voltage
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Two microwave ovens are connected to the same type of wall outlet, with a voltage of 230 V. Despite that, they run with different power. What does that mean?
Philip uses his microwave oven to heat his tea water. It takes about two minutes for the water to reach boiling point. Jenny also has a microwave oven, but it only needs one minute and twenty seconds to heat the same amount of water. How can her 'mike' heat the water faster? That's because Jenny's microwave oven has a higher electric power than Philip's.
Electric power is a measurement of how fast an electric device uses electricity. Power is measured in a unit called 'Watt' - which we write as a capital 'W'. Jenny's microwave oven has a power of 1,200 Watts. Philip's has only 800 Watts. The higher the power, the faster you can heat things in the oven.
What factors affect electric power output? If a device has electric current passing through it, that means that electrons are moving through it. If more electrons pass through the device every second, we say that it has higher current. Higher current leads to higher power. The electrons can have a stronger or weaker "urge" to get through the device.
This is the voltage. Higher voltage means that each electron is being "pulled" more strongly, which... also leads to a higher power output. The power is dependent on both the current and the voltage. The power - the number of Watts - is calculated by multiplying the current - in Amperes - by the voltage - in Volts.
Let's look at a couple of examples! Here's a small torch, with a 1.5 Volt battery. The power of the torch is 3 Watts. Can we calculate what current runs through it? The power - 3 Watts - is...
the voltage - 1.5 Volts, times the current, so it's got to be... 2 Amperes. 1.5 Volts times 2 Amperes equals 3 Watts. Here's a larger torch, with more batteries, together giving a voltage of 6 Volts. It has a power output of 9 Watts, that is, three times as much as the smaller torch.
How strong is the current? What do we need to multiply 6 Volts by, to get the result: 9 Watts of power? That's right, one-point-five. This larger torch has the current: 1.5 Amps running through it. The torch that shines more strongly - with a power of 9 Watts, has a lower current - fewer electrons moving through it every second.
But the voltage is higher, so each electron has a stronger "urge" to get through. That makes the power higher in this torch, even though the current is lower. Electric power equals current times voltage. The higher the power, the faster a device uses electrical energy. And that means that the tea water gets hot, in a shorter time.