1P May 2015 Flashcards
What is alternating current?
A current which changes direction continuously.
Hooke’s law?
Extension is directly proportional to force.
How can you show the shape of a magnetic field around a bar magnet?
Mark the line, moving the compass to a new point along the line. Start a new line from a different place.
Pressure as …
force on an area.
How does a decrease in pressure outside a balloon affect the hot air inside?
Hot air escapes from balloon.
Explain why a hard drive works at a lower temperature when the black drive is on top of the white drive.
Transfer between the two is conduction. Emission of thermal energy. Black loses more heat than white, because black is a good emitter.
Why does the activity of a radioactive sample reduce with time?
Activity is due to nucleus decaying.
Uses of total internal reflection?
Optical fibres for communication, prism in camera.
Equation linking critical angle and refractive index?
sinc = 1/n
How to obtain a value for speed of sound?
Method to make a sound large enough, speed=distance/time, still air, repeat and average, reset stopwatch for each value.
What is the need for a variable resistor?
To control the current.
