Electric and Magnetic fields

Question 1

Charge

Answer 1

a quantifiable property which relates to how strongly an object is affected by an electric field

Question 2

Electric field strength

Answer 2

a measure of the electric force that acts per unit of charge at a point in space

Question 3

Bar magnet

Answer 3

a permanent magnet in the shape of a prism

Question 4

Electromagnet

Answer 4

a magnet created by an electric current

Question 5

Magnetic field

Answer 5

a vector field that arises from the movement of charge

Question 6

Permanent magnet

Answer 6

an object with material properties that cause it to produce a magnetic field

Question 7

Solenoid

Answer 7

an electromagnet made from coils of wire

Question 8

Static field

Answer 8

a field that is not changing over time

Question 9

Conventional current

Answer 9

current that is assumed to consist of flowing positive charges so that the direction of current is the direction a positive charge would move

Question 10

DC (direct current) Electricity

Answer 10

electricity with a constant direction of current and voltage

Question 11

Slip Rings

Answer 11

a component used to maintain a constant electrical connection between a stationary external circuit and a rotating coil

Question 12

Slip Ring Communtator

Answer 12

a component used to reverse the electrical connection between a stationary external circuit and a rotating coil every half rotation

Question 13

Draw a diagram of a single positive and negative charge

Answer 13

Question 14

Draw a diagram of two positive and negative charges

Answer 14

Question 15

Draw a diagram of one postive and one negative charge

Answer 15

Question 16

What is the formula for calculating electric field strength around a point charge?

Answer 16

Question 17

What is the formula for calculating the electric force acting on a charge?

Answer 17

This equation is equivalent to F_g = mg in the context of gravitational fields. And is given by:

F=qE

Where F= the electric force (N), q= the electric charge experiencing the force (C) and E= the electirc field strength (NC^-1 or Vm^-1)

Question 18

What is the formula for calculating the force on two-point charges? (Columbus formula)

Answer 18

Question 19

What is the formula for finding the strength of a uniform electric field?

Answer 19

Question 20

What is the two formulas for the work done within a uniform electric field?

Answer 20

Question 21

What are linear particle accelerators?

Answer 21

Scientists use electric fields between two plates to accelerate particles like electrons and protons up to very high speeds. This may also be referred to as an electron gun.

Question 22

Requirements of a permanent magnet and an electromagnet

Answer 22

A permanent magnet has a

static field if the magnet itself is stationary and a changing field if the magnet is in motion.

whereas

an electromagnet has a static field if the current is constant and the electromagnet is stationary. An electromagnetic has a changing field if the current is changing or the electromagnet is in motion.

Question 23

Diagram of magnetic field patterns around bar magnets

Answer 23

Question 24

Diagrams of magnetic field patterns around loops

Answer 24

Question 25

Diagram and description of magnetic field patterns around solenoids

Answer 25

Question 26

What does the direction of a current around a solenoid determine?

Answer 26

The direction of the current around the solenoid determines the direction of the field, which means that the way that a solenoid is coiled and the orientation of the current source must be considered when determining field direction.

Question 27

What are the conditions for a magnetic force on a charged particle?

Answer 27

When moving through a magnetic field, a charged particle will experience a force which is dependant on the angle between its direction of motion and the magnetic field lines.

The magnetic force is at its maximun when the direction of its motion is perpendicular (right angle) to the magnetic field lines.

There is no magnetic force when the direction of motion is parallel to the magnetic field lines or if the particle is stationary.

Question 28

The formula for finding the magnitude of the magnetic force on a charged particle

Answer 28

F=qvB

Where F = magnitude of magnetic force (N), q = magnitude of charge (C), v = speed of particle (m s−1), B = magnetic field strength (T)

Make sure the direction of motion is perpendicular to the magnetic field.

Question 29

The formula for circular motion within a magnetic field

Answer 29

Question 30

Formula for finding the magnitude of magnetic force on a current-carrying wire

Answer 30

Question 31

What does a DC motor consist of?

Answer 31

• a constant DC voltage supply - which is used to produce a direct current.
• a split ring commutator - which is used to transmit the direct current to the coil in a way that allows continuous rotation.
• a coil of wire - made of one or more windings of a current-carrying conductor that will experience a force due to the magnetic field and freely rotates.
• a magnetic field - produced by either permanent magnets or electromagnets to create a force on the coil of wire.

Question 32

Diagram of a simple DC motor. (labelled)

Answer 32

Question 33

What is the role of the split ring commutator within a DC motor?

Answer 33

Question 34

What is the role of a DC motor

Answer 34

A DC motor converts electrical energy into kinetic energy.

Question 35

What occurs in a DC motor if slip rings are used instead of a commutator?

Answer 35

A DC motor will not be able to complete full rotations if slip rings are used instead of a split ring commutator. The motor will oscillate and then get stuck in the vertical position if there is a horizontal magnetic field).