Topic 1: Electric Fields

Which particles are negatively charged?

electrons

Which particles are positively charged?

protons and positrons

The atomic nucleus comprises which particles?

protons and neutrons

What type of particle/s “flow” in solid wires to create electric current?

the negatively charged electrons move while the positively charged protons don’t move

The atom is held together by the attractive electric force between the ______ ______ in the nucleus and the _____ _____.

positive protons, negative electrons

_____ and ____ have charges of opposite sign but exactly equal magnitude.

Electrons, protons

What happens when John Travolta rubs his foot on the carpet and then touches the door knob? Why?

He gets shocked because the electrons jump from him to the doorknob. When he rubs his foot, the electrons jump from the carpet to his foot. The electron affinity of John’s rubber sole is greater than the carpet, so the electrons are jumping from the carpet to John The more he rubs his foot, the more electrons jump onto his body. As the extra charge builds up, it isn’t happy because the negative charges of teh electrons all repel each other and push against each other and this results in voltage bias.

What happens when you rub a balloon against something and then touch it to a wall? Is the balloon and/or wall charged?

The electrons jump from the sweater to the balloon, the balloon becomes negatively charged as it’s gained electrons and the sweater is positively charged because it has lost electrons, so then if we release them they are attracted to each other, opposites attract each other. The wall is neutral. The negative charge of the balloon induces a dipole and so that causes the balloon to stick to the wall due to the charge separation caused by all of these negative charges.

Attraction between _____ balloon and _____ hair. _____ move from hair to balloon.

negative, positive, electrons

When two ______ materials touch each other, then _____ can ______ from one object to the other, (Do NOT have to rub!)

different, electrons, move

The objects then have _______ charges that are opposite. One object become negative and the other positive.

unbalanced

Opposite charges _____.

attract

Like charges ____.

repel

Electrons are free to move in ______ but not in ______.

conductors, insulators

In solids, _____ don’t move.

protons

Negative electrons can travel through a metal ______, but not through an ______. Protons do ____ move in solids!

conductor, insulator, NOT

If charged objects are connected with a ____, then electrons can move and _____ _____ between the objects,

conductor, evenly distribute

If charged objects are connected with an insulator, then the charge _____ ____.

cannot move

Electrons move from rabbit fur to amber. What is charge on fur? On Amber?

fur is positive and amber is negative

What is Greek word for Amber?

Electra

Electric current is in direction of _____ flow.

positive

Electric current is due to the flow of ______.

electrons

The ______ of the electrostatic force between point charges is determined using Coulomb’s Law.

magnitude

The ______ of the force is determined: opposites attract/likes repel.

direction

An _______ is said to exist in a region of space around a charged object (source). The field exerts a force on the other charged objects in the region.

electric field

The _______ of the field is defined to be the direction of the electric force that would be exerted on a small positive test charge placed at that point.

direction

______ and ______ forces are both field forces.

electric, gravitational

Is electric field a vector?

Yes

The electric field due to a point charge points ___ from positive charges and ______ negative charges.

away, towards

The electric field acts on the ______ due to other charges, not the charge itself.

charge

How would you answer this question? : Which vector describes the electric field that acts on the -3C charge?

electric field points away from positive and towards negative

For vectors regarding forces, what rules do we follow?

opposite charges attract and like charges repel

How would you answer this question? : Which vector describes the resultant force?

opposite charges attract and like charges repel

For electric field lines, we start at _____ charges or infinity.

positive

For electric field lines, we end at _____ charges or infinity.

negative

Density of lines (more lines in small area) indicate a _____ electric field.

larger

Separated electric field lines show a ____ electric field.

weaker

The greater density of the electric field lines, the ____ the electric field.

stronger

Electric field tells you direction of field if charge is _____, if ______ then force will point in opposite direction of electric field.

positive, negative