Physics S2 Flashcards
How do you magnetise a Steel or Iron bar?
Place a steel bar into a cardboard tube, pass a direct current around it, then pull out the bar. The strong magnetic field inside the tube magnetises the steel bar. You can test it by using it to pick up some iron filings.
How do you demagnetise a Steel or Iron bar?
To demagnetise the bar use an alternating current.
Simple Cell?
A simple cell is composed of two rods (electrodes) of different metals, copper and zinc, connected by a wire at one end. The other ends of the wire dip into an acid solution. Current flows through the wire. Hydrogen bubbles insulate the plates. The zinc slowly dissolves into the sulphuric acid and bubbles of hydrogen form on the copper plate. In the simple cell, the action of the acid on the zinc results in the production of electrical energy.
What is a Dry Cell?
A Dry cell is a type of electricity-producing chemical cell, commonly used today for many home and portable devices, often in the form of batteries. A dry cell produces current for a longer time than simple cell. A gel is needed to replace any liquids. Chemical reactions make a current. Hydrogen gas is made but is quickly removed by a depolarising agent. Some cells can be recharged by passing a DC into them e.g. mobile phones etc.
Reflection from a mirror?
When light rays reflect from a mirror, they obey the law of reflection: the angle of incidence equals the angle of reflection.
The normal is a line drawn at right angles to the reflector.
The angle of incidence is between the incident (incoming) ray and the normal.
The angle of reflection is between the reflected ray and the normal.
Refraction?
Sound waves and light waves change speed when they pass across the boundary between two substances with different densities, such as air and glass. This causes them to change direction and this effect is called refraction.
Refraction at 90 degrees?
There is one special case you need to know. Refraction doesn’t happen if they cross the boundary at an angle of 90° - in that case they carry straight on.
What happens if a light ray hits the perspex at an angle?
If a light ray hits the perspex at an angle, its speed and direction changes and the ray is bent back into its original direction when it leaves the block.
Total internal reflection?
Waves going from a dense medium (glass) to a less dense medium (air) speed up at the boundary. This causes light rays to bend when they pass from glass to air at an angle other than 90º. This is refraction.
Beyond a certain angle, called the critical angle, all the waves reflect back into the glass. We say that they are totally internally reflected.
What is lateral inversion in mirrors?
Lateral inversion is the visual illusion that left and right sides of a mirror image are switched. A person looking in a flat plane mirror who raises his right hand sees his mirror image’s left-side hand raise.
The pinhole camera?
A pinhole camera consists of a box or tube with a translucent screen at one end and a tiny hole (the pinhole) made in the other end. Light enters the box through the pinhole and is focused by the pinhole onto the translucent screen. The image is upside down and smaller than the object.
Converging lenses?
A lens is transparent block that causes light to refract (changes the direction the light travels in). A converging lens (or convex lens) is curved on both sides. This means the light rays coming out of it come together at a point – they converge.
