Electric and Magnetic Forces

What is a force

• A pull exerted on an object

• a measure of how heavy an object is

• a push or a pull exerted on an object

• a change in the direction of motion of an object

The diagram shows a device called a capacitor. In a capacitor, metal plates are separated by an insulating material that keeps charges from transferring between the plates. By running current through the wires, the two parallel metal plates within the capacitor become oppositely charged. Note that only the top metal plate is shown in the diagram.

Which two choices correctly explains what changes in strength occur in the electrical force between the plates?

• Reversing the wires to switch the charges on the plates and increasing the thickness of the plastic coating is no change in strength

• Increasing the thickness of the insulating material and Decreasing the current in the wires is a increase in strength

• Decreasing the current in the wires and reversing the wires to switch the charges on the plates is a decrease in strength

• Decreasing the current in the wires and increasing the thickness of the insulating material is a decrease in strength

Jesse tests three magnets by observing how many paper clips he can attach to the north pole in a single chain. He finds that Magnet A holds six paper clips, Magnet B holds five paper clips, and Magnet C holds two paper clips. He warms Magnets A and C in the oven for a few minutes and repeats his procedure. This time, Magnet A holds only four paper clips, Magnet B still holds five paper clips, and Magnet C cannot hold any paper clips. Which statement explains Jesse’s observations?

• The poles of the magnet become reversed when warmed and cause it to repel the paper clips.

• Warming a magnet causes the distance of its magnetic force to decrease

• The forces produced by a magnet naturally become weaker over time.

• Warming a magnet unaligned some of the magnetic domains.

How can you change the direction of electric current in an electromagnet?

• Observe how a magnet moves when brought near the end of the nail

• Observe how many paper clips can be attached to the end of the nail

• Connect wires to two batteries like before

• Connect wires to the opposite ends of the batter like before

What relationship is shown in the picture?

• Magnetic force between opposite ends is attractive

• Electric force between like ends is attractive.

• Magnetic force between like ends is attractive.

• Electric force between opposite ends is attractive.

Kim has a loop of wire and a magnet. Which of these will create the largest electric current in the loop?

• Wrap the wire tightly around the magnet.

• Place the magnet in the center of the wire

• Move the magnet quickly through the loop

• Spin the loop of wire slowly above the magnet.

What do the field lines point to? What effect does spacing between the field lines create?

• The field lines point to the direction gravity travels. The more space between the lines means the force is weaker.

• The field lines point to the direction electrons travel. The less space between the lines means the force is stronger.

• The field lines point to the direction charges travel. The less space between the lines means the force is stronger.

• The field lines point to the direction gravity travels. The more space between the lines means the force is Stronger.

A balloon is rubbed with a piece of cloth. Which statement describes the charges shown?

• Negative charges appeared when the cloth was rubbed on the balloon.

• Some of the positive charges on the balloon disappeared when it was rubbed by the cloth.

• Negative charges from the cloth were transferred to the balloon.

• Balloons always have more negative charges than positive charges.

Sachs finds that the end marked A tips downward until it is touching the end marked D. Which test allows Sachs to draw a conclusion about the magnetic properties of each metal bar?

• She hangs A above the center of bar CD and finds that A is only weakly attracted to CD. She concludes that bar CD always produces a magnetic field, but bar AB only temporarily produces a magnetic field.

• She hangs A directly above C and sees that the two ends attract. She concludes that both bar AB and bar CD always produce magnetic fields.

• She hangs B directly above C and sees that the two ends attract. She concludes that both bar AB and bar CD always produce magnetic fields.

• She hangs B directly above C and sees that the two ends attract. She concludes that bar CD always produces a magnetic field, but bar AB only temporarily produces a magnetic field.

Which description of the charges is correct?

• Object A is negatively charged and sending its charges to B which is positively charged.

• Objects A and B are both positively charged.

• Object A is positively charged and its field lines are flowing towards Object B which is negatively charged.

• Object B is neutral and is collecting charges.