Electricity and Magnetism

Magnetic Field Around a Loop of Wire

Using current and the left-hand rule to predict the field of a current loop

Magnetic Field Around a Loop of Wire lesson illustration

What's wrong with this picture?

Magnetic Field Around a Loop of Wire lesson illustration

 

 

Flux lines never touch

 

"My Magnet Attracting Money"

'Did you know that US currency is attracted to a magnet? There are iron particles in the ink that is causes this attraction.' Rob Gallagher
Rob the 'MagnetNerd'

 

Making a Magnet
with Electricity

Electric Magnets are created using
thousands of wire loops

 

[ Flash ]

 

 

We can understand an electric magnet
 by understanding the magnetism
of a single loop of wire

 

 

Ex 3) Magnetic field around a Single Loop of Wire w/ current

 

[ Flash ]

 

Magnetic Field Around a Loop of Wire lesson illustration 

A loop of wire with current
creates a little magnet

 

North Pole is either
above or below the loop

 

 

 

 

Finding N. and S. Pole
of a loop of wire


Step 1 - Current travels from (-) to (+)  terminal, DRAW the direction of the current on the wire

 

Step 2 - Palms away, thumb in direction of current

 

Step 3 - Curl fingers of left hand into loop

Why Left and not right??

 

Step 4 - Note where four fingers tips are pointing when they enter the INSIDE of the loop

 

Fingers tips - NORTH POLE of the magnetic field

 

 

 

 

 

 

Magnetic Field Around a Loop of Wire lesson illustration

 

North Pole
 ABOVE or BELOW ??

 

 

Below


South Pole??
ABOVE or BELOW??

 

 

Above

 

 

 

 

 

Magnetic Field Around a Loop of Wire lesson illustration 

North Pole
 ABOVE or BELOW ??

 

Below

 

 

 

 

 

 

 Magnetic Field Around a Loop of Wire lesson illustration

North Pole
 ABOVE or BELOW ??

 

 

Above

 

South Pole
 ABOVE or BELOW ???

 

 

Below

 

 

 

 

If (+) and (-) terminals are reversed
the current is reversed.

 

Magnetic Poles?

 

Poles are reversed

 

 

Using magnets to
repel crocodiles








 

Check Your Understanding

5 quick questions — pick an answer to see if you’re right.

1. A single loop of wire carrying current acts like:

2. In the left-hand rule for a loop, the fingertips point into the inside of the loop. Where they point is the:

3. A loop lies flat on a table. Viewed from above, electron current flows clockwise. Where is the north pole?

4. The battery's (+) and (−) terminals connected to a loop are switched. What happens to the loop's magnetic poles?

5. A strong magnet can pick up a US dollar bill. Why?

Solenoids →