Lesson 2 Wires carrying current close to each

�A – higher density of field lines, greater B, greater Fm – lower density

� Magnetic lines of force are continuous � The direction of a magnetic field

The Earth’s magnetic field is similar to a bar magnet The field is

When current flows through each loop of wire in a coil a magnetic

the current goes in the same direction for each wire the magnetic field

Fingers curl around the coil in the direction of the electron flow. Outstretched

Is the direction of the current shown, e¯ flow or conventional current?

Need to use right hand to B field direction as shown: ∴ is

�A solenoid can be made to be a much stronger magnet by placing a

Ampere investigated the interaction between two current-carrying wires parallel to each other. What

The direction of the fields is different therefore the fields attract each other.

� Current is the rate at which e¯ flow through a wire. � Units:

The B field around a current carrying wire depends in part on the

If two wires, each one meter long and one meter apart, carry current

A 30 cm long wire is placed in a 0. 50 T B

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Lesson 2 : Wires carrying current close to each other.

�A – higher density of field lines, greater B, greater Fm – lower density of field lines, lesser B, lesser Fm A �B � Greatest density of field lines is near the poles of a magnet B

� Magnetic lines of force are continuous � The direction of a magnetic field line outside a magnet is N to S and inside is from S to N

The Earth’s magnetic field is similar to a bar magnet The field is the result of the fluid motion of iron within the earth’s core (read text for new theories)

When current flows through each loop of wire in a coil a magnetic field is set up in such a way that it makes the coil act like a single bar magnet. - the magnetic field around a straight wire is very weak - to make the field stronger, we can bend the wire into many loops

the current goes in the same direction for each wire the magnetic field of each wire adds up to create a much stronger field

Fingers curl around the coil in the direction of the electron flow. Outstretched thumb points to the end of the coil that acts as the north end of a fixed magnet.

Is the direction of the current shown, e¯ flow or conventional current?

Need to use right hand to B field direction as shown: ∴ is conventional current.

Determine position of each compass

�A solenoid can be made to be a much stronger magnet by placing a ferromagnetic material (usually steel) inside the coil. � Electromagnets have many uses. � Magnetizing ferromagnetic material � Bells � Relay switches

Changes current to another circuit

Ampere investigated the interaction between two current-carrying wires parallel to each other. What is the effect on the wires?

The direction of the fields is different therefore the fields attract each other. If the field directions are the same they would repel.

� Current is the rate at which e¯ flow through a wire. � Units: C/s or ampere (A) � Symbol: I

The B field around a current carrying wire depends in part on the current in the wire. F = magnetic force (N) I = current (A) or (C/s) l = length (perpendicular to B) B = magnetic field strength in tesla (T)

If two wires, each one meter long and one meter apart, carry current so that the force between the two wires is 2. 00 x 10 -7 N, the current in each wire is one ampere.

A 30 cm long wire is placed in a 0. 50 T B field that is directed out of the page. The e¯ flow is to the right, with a current of 1. 2 A. Determine the force acting on the wire.

What is the direction of the force?