Unit 3 Science

If 2 objects attract each other, their charges could be:

• positive, positive
• negative, negative
• positive, negative

The following is an example of an electrical conductor:

• copper
• plastic
• rubber
• wood

The following is an example of an insulator:

• copper
• iron
• rubber

What is electric current?

• a material's opposition to the flow of electric charge
• the rate at which electric charges pass a given point
• the number of charges that pass a given point
• the amount of work to move a unit of electric charge between 2 points

Which of the electric devices listed below uses mostly alternating current?

• dishwasher
• flashlight
• mp3 player
• digital camera

Peter's teacher tells him that he should not place his electric stereo near the edge of a pool because the water in the pool is a conductor. What does she mean when she says that the water is a conductor?

• Water is a type of electrical energy.
• Water damages electric circuits. 
• Electric charges cannot flow without water.
• Electric charges move through the water in the pool.

Most strings of lights are wired in a parallel circuit. Which of the following is the best reason why a string of outdoor lights should be wired in a parallel circuit and not a series circuit?

• Parallel circuits are safer to use than series circuits.
• The lights in a parallel circuit will light up brighter than the lights in a series circuit.
• If one light in the string burns out in a parallel circuit, the rest of the lights will continue to shine.
• You need to use more wires to construct a series circuit than a parallel circuit.

Which of the following best describes how a powerful electromagnet could be used in a junkyard?

• It could move heavy objects made of iron.
• It could convert electrical energy into mechanical energy.
• It could light up the area so workers can see at night.
• It could provide a voltage source for old electronic equipment.

The interaction between electricity and magnetism is:

• electromagnetism
• ferromagnetic
• magnetic field
• static electricity

In an alternating current, charges flow in the same direction.

• true
• false