Magnetism

• Created by: SamFuller
• Created on: 12-10-18 17:41
• Magnetism
• Poles
• Magnetic definition - Materials attracted by a magnet.
• Iron
• Zinc
• Nickel
• North-Seeking Pole definition - The end of a magnetic that points North
• South-seeking Pole - The end of a magnetic that points South
• Magnetism on Objects is the greatest near the poles
• Magnetic Fields
• Poles
• Magnetic definition - Materials attracted by a magnet.
• Iron
• Zinc
• Nickel
• North-Seeking Pole definition - The end of a magnetic that points North
• South-seeking Pole - The end of a magnetic that points South
• Magnetism on Objects is the greatest near the poles
• There is a Magnetic field around a magnet.
• There is an affect of magnetic materials and other magnets in this area
• It is convention to draw magnetic field lines coming from North to South
• Permanent and induced Magnetism
• A permanent magnet produces its own magnetic field
• An induced magnet becomes magnetic when it is in a magnetic field
• The Magnetic field of a straight wire
• A current in a wire produces a magnetic field
• Right-hand grip rule: Line your thumb up with the direction of current. The way your hands curl gives you the magnetic field lines direction
• A cross shows current into the paper
• A dot shows cureen out of the paper
• Solenoids
• A long coil of wire which has a high combined Magnetic Field
• To increase the strength    1. Increase Current           2. More coils   3. Closer coils                4. Iron core in the centre
• Magnetic fllux density
• The number of lines of magnetic flux in a given area
• Force on a wire = magnetic flux density (teslas) x current x length
• A magnetic field acts on a wire to repel it.
• The size of the force depends on the flux density, the sixe of the current
• Left Hand rule: First finger pints in direction of field lines. Second finger points in direction of current. Thumb gives force direction
• Direct Current Motors
• A coil with a current on an axis in a magnet will rotate. This is because current is travelling in alternate directions on each side
• Kept rotating with a split-ring commutator
• Induced P.D.
• When a wire moves through a Magnetic Field it induces a p.d.
• If the wire is in a creat circuit a current is induced
• Changing the direction of movement changes the direction of the p.d.
• This is the generator effect
• Induced P.D. with Coils
• Induced P.D.
• When a wire moves through a Magnetic Field it induces a p.d.
• If the wire is in a creat circuit a current is induced
• Changing the direction of movement changes the direction of the p.d.
• This is the generator effect
• Moving a magnet near a coil of wire induces a p.d.
• As the north pole moves towards the coil the current flows in a way the nearest pole becomes a north pole repelling the magnet
• As the magnet is repelled the direction of cuurent changes and the nearest pole becomes a south pole attracting the magnet back
• Alternators
• 1. The coil is vertical. In this position the sides are parallel to the field and there is no p.d.
• 2. The coils is horizontal. The current cuts through the field at the greatest rate the induced p.d. is at its maximum
• 3. The coils is ertical again. There is no p.d.
• 4. The coils is horizontal again. The sides are opposite to 2. and so the p.d. is at the maximum in the alternate direction