Explain what is

happening off camera

to create what you see

in the video below.

When the current is turned on, the electromagnet's N pole attracts the S pole of the compass. When the current is reversed, the poles are reversed.

Electric Bell

Name the major parts of an electric bell.

What is the function of part C?

Electric Bell

Source: Elroy M. Avery School Physics (New York: Sheldon and Company, 1895) 556

E - Electromagnet, H - Striker, P - Switch

C - When the striker is attracted to the electromagnet, the circuit is opened and the striker returns to its initial position

Click on the picture below
to activate a larger version of this animation

St. Mary's H.S.

Ex 4) Magnetic field around Solenoid (Electromagnet)

(conductor arranged in a coiled pattern)

North and South Pole
at either end of the core.

1. Determine North and South pole with ...

a) North Pole of a Compass

b) 2nd Left Hand Rule

Step 1 - Current travels from
(-) to (+) terminal

DRAW the direction of the current on the wires

Step 2 - WITH PALMS AWAY, point the fingertips of left hand in direction of current

Step 3 - Thumb - North Pole!!

North Pole - RIGHT or LEFT???

Right

North Pole - Top or Bottom?

Bottom

North Pole - Right or Left?

Left

Strength of a magnetic fieldof a solenoid can be increased by:

1) Increasing or decreasing the number of turns? (of wire)

Increasing

2) Increasing or decreasing current?

Increasing

3) inserting a highly permeable core (increases flux density)

high permeable cores

- Nickel, Iron, Cobalt,

These materials tighten existing flux lines, do not increase # of flux lines

low permeable cores

- air (Pulling out the core)