Magnetism
­ a property of certain metals or electric currents that produce magnetic forces
Atomic Reason for Magnetism
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Magnet Facts
2 poles
Poles are defined
Attract / Repel
Break a magnet in half
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Compass
is this compass pointing north
Homemade Compass
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The earth as a magnet
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Dynamo
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Pole Reversal
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Magnetic Fields
­ The region around a magnetic object where magnetic forces can be detected
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Electromagnetic Induction (induced emf)
­ The creation of a potential difference (emf) by moving a wire through a magnetic field
How it works
similar to a battery
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4 Things that affect the induced potential
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MAGNETISM
A student sprinkled iron filings around a bar magnet and observed that the filings formed the pattern shown below. The magnetic field is strongest at point
(1) A
(2) B
(3) C
(4) D
The diagram below represents the magnetic field near point P. If a compass is placed at point P in the same plane as the magnetic field, which arrow represents the direction the north end of the compass needle will point?
The diagram below shows a wire moving to the right at speed v through a uniform magnetic field that is directed into the page. As the speed of the wire is increased, the induced potential difference will
(1) decrease
(2) increase
(3) remain the same
In order to produce a magnetic field, an electric charge must be
(1) stationary (3) positive
(2) moving (4) negative
The diagram below shows a bar magnet. Which arrow best represents the direction of the
needle of a compass placed at point A?
(1) ← (3) ↑
(2) → (4) ↓
Which diagram best represents magnetic flux lines around a bar magnet?
15 The diagram below shows the lines of magnetic force between two north magnetic poles. At which point is the magnetic field strength greatest?
(1) A (3) C
(2) B (4) D
21 The diagram below represents a 0.5­kilogram bar magnet and a 0.7­kilogram bar magnet with a distance of 0.2 meter between their centers.
Which statement best describes the forces between the bar magnets?
(1) Gravitational force and magnetic force are both repulsive.
(2) Gravitational force is repulsive and magnetic force is attractive.
(3) Gravitational force is attractive and magnetic force is repulsive.
(4) Gravitational force and magnetic force are both attractive.
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The diagram below represents a wire conductor, RS, positioned perpendicular to a uniform magnetic field directed into the page. Describe the direction in which the wire could be moved to produce the maximum potential difference across its ends, R and S. [1]
A student is given two pieces of iron and told to determine if one or both of the pieces are magnets.
First, the student touches an end of one piece to one end of the other. The two pieces of iron attract. Next, the student reverses one of the pieces and again touches the ends together. The two pieces attract again. What does the student definitely know about the initial magnetic properties of the two pieces of iron? [1]
The diagram below shows two compasses located near the ends of a bar magnet. The north
pole of compass X points toward end A of the magnet. On the diagram provided in your answer booklet, draw the correct orientation of the needle of compass Y and label its polarity. [1]
59 On the diagram of a bar magnet in your answer
booklet, draw a minimum of four field lines to show the magnitude and direction of the magnetic field in the region surrounding the bar magnet. [2]
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Summary Facts
1.) likes repel, opposites attract
2) compasses follow field lines (N of compass repels from north side of compass, out from north)
3.) Moving electric charges create magnetic fields
4) Wires 'cutting' across field lines move charges to create voltage (potential diff).
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