Electricity and Magnetism

Warmup 10-15-07Static Electricity

Explain what is happening in this picture using the following vocabulary words:

Atoms: protons electrons

Charge:

negative

positive

Repel Attract

Explanation

Atoms usually contain an equal amount of protons and electronsProtons have a positive charge; electrons have a negative charge

Explanation

Sometimes atoms lose electrons. They then have a positive charge. The electrons get added to other atoms, which then have a negative charge.

Explanation

The negatively charged atoms are strongly attracted to positively charged atoms.

Electrons jump from a negatively charged surface to a positively charged surface.

Notes: Electrostatic Fields

Coulumb’s LawThe strength of an electric field is determined by two things:

1. the strength of the charges

2. the distance between the two charges

Notes: Electrostatic Fields

F = k (q1 X q2) / d

To find Field strength, multiply the charges and divide by distance.

IN OTHER WORDS:

The more charge, the stronger the force.

The closer the charges, the stronger the force.

Coulumb’s Law

Which point is in the strongest part of the field?

Notes: Electrostatic Fields

The closer the charges, the stronger the force.

The more charge, the stronger the force.

Coulumb’s Law

Which pair of charges create the strongest field?

Warmup 10/15/07

Which tool best measures the amount of current that will be induced in the wire coil?

Which tool can be used to measure the direction of current that will be flowing in the wire?

Which tool can be used to measure the amount of thermal energy converted from the electrical energy flowing in the wire?

The diagram shows a magnet being inserted into a wire coil.

magnetic compass light meter thermometer voltmeter

Notes - Current Flow

The RIGHT HAND RULE:The thumb points in the direction of the current; the fingers in the direction of the magnetic field.

Test yourself:

The current is flowing in the direction the thumb is pointing. What is the direction of the magnetic field?

1 2 3 4

Test yourself:A compass placed on the right side of the current flowing through the wire points North.

Predict the direction that the compass will point to on the left side of the current flowing.

Explain why, citing experimental evidence (what you have seen in activities.)