June 2013 Flashcards
How to use the activity of a radioactive source?
- Use a rate meter.
- Measure background radiation.
- Use a safety precaution.
- Repeat.
What does 30W say about the energy transfer?
Power. Rate of energy transfer.
How do step down transformers work?
Primary and secondary coil. Iron core. Primary has more coils.
Celsius to kelvin?
Add 273.
What happens to particles in a liquid when it boils?
- Particles move apart.
- Particles gain energy.
- Particles leave liquid.
Why do shiny surfaces reduce thermal energy transfer?
Reflection, poor emission.
Why does a substance without a lid still not lose heat?
- Air insulates surface.
- Cold air above the liquid.
Why does the load slide to the front when a lorry stops suddenly?
When lorry stops it still has momentum, lorry stops in a shorter time.
Why does more weight increase near the front of the lorry when the weight slides to the front?
Center of gravity is nearer the front. Clockwise and anticlockwise moments are equal.
What is the visible spectrum?
A sequence with the colours identified.
What colour has the longest wavelength?
Red.
Why is electricity transmitted at high voltages?
- Low current.
- P = IV.
- Less energy is lost.
- More efficient.
What does 50Hz alternating current mean?
Current which changes direction 100 times per second.
Why does d.c from the generator must be changed tp a.c before it is transmitted?
Transformers change the voltage. Transformers use alternating current.
