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Lesson · Grade 6 · Applied Design, Skills and Technologies

Power: How Fast Energy Changes Form

  • Grade 6
  • Applied Design, Skills and Technologies
  • 1 min 16 s
  • British Columbia
  • BC6-AD-29

A dim bulb and a bright bulb of the same kind are timed side by side: in one second the dim bulb changes 25 joules of electrical energy into light and heat, and the bright bulb changes 100 joules, four times as fast. Dividing energy by time gives their power, 25 watts and 100 watts, which stays the same over 10 seconds, so power is how fast energy changes form, measured in watts.

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In one sentence

The question this lesson answers

Why is one bulb brighter than another bulb of the same kind?

Each bulb changes electrical energy into light and heat.

Transcript

What the lesson says

Why is one bulb brighter than another bulb of the same kind?

Each bulb changes electrical energy into light and heat.

In one second, the dim bulb changes 25 joules and the bright bulb changes 100 joules.

So the bright bulb changes energy four times as fast.

Power is how fast energy changes from one form to another.

To find power, divide the energy by the time it takes.

Power is measured in watts, and one watt is one joule per second.

For the dim bulb, 25 joules divided by 1 second is 25 watts.

For the bright bulb, 100 joules divided by 1 second is 100 watts.

In 10 seconds, the dim bulb changes 250 joules and the bright bulb changes 1000 joules.

Divide each by 10 seconds, and you still get 25 watts and 100 watts.

For bulbs of the same kind, more watts means a brighter bulb.

Power is the rate at which energy changes form, and we measure it in watts.

Curriculum

Where this fits

British Columbia, Grade 6

Applied Design, Skills and Technologies, Power technology: power is the rate at which energy is transformedBC6-AD-29

Next: Forms of Energy: Moving and Stored

The outcomes and strands follow the British Columbia curriculum.

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