Ch.6 Electricity & Magnetism

What is the current in a 20 ohm electric heater operated at 240v?

12 A

What is the voltage needed to produce a current of 12 A in a resistance of 20 ohms?

240 v

What is the resistance in a 24 W, 12 v light bulb?

6 ohms

Three 12-V batteries cannot be connected to give a voltage for the set of

6 v

Which particle is the easiest to remove from an atom?

electron

A compass needle tends to do what?

line up parallel to a magnetic field

An atom consists of what?

a small positive nucleus surrounded at a distance by electrons

When a magnetized iron bar is strongly heated, its magnetic field does what?

becomes weaker

In a drawing of magnetic field line, the stronger the field is, the

closer together the field lines are

When does an object have positive electric charge?

it has a deficiency of electrons

What is true about a positive electric charge?

it repels other positive charges

Superconductivity occurs in certain substances under what circumstances?

only at very lower temperature

A molecule that has lost an electron becomes a

positive ion

The volt is the unit of electric

potential difference

A magnet attracts

some substances and repels others

Relative to the electric force between two protons, the gravitational force between them is what?

weaker