Homework Questions
1. What is the unit for measuring energy?
2. What form of energy is usually wasted?
3. Grace is watching a video on a laptop. The laptop is running from its battery and feels warm to the touch. Fill in the missing forms of energy for the laptop:
______________ –> ____________ + sound + heat
4. Nathan uses a ski lift. The electric motor moves the chairs up the mountain and drops the skiers at the top. Fill in the missing forms of energy for this process:
_______________ –> kinetic (movement) –> ______________ –> _______________ potential energy
5. (a) A torch is fitted with a standard light bulb. Its cells supply 30 J of energy, of which 4 J are given off as light. The rest of the energy is wasted as heat. Calculate the efficiency of the bulb.
(b) A second torch is fitted with an LED bulb. Its cells only supply 15 J of energy but 4 J are given off as heat. What does that tell us about the efficiency of the LED bulb compared to the standard bulb in (a)?