Chapter 24

Question 1

What is a Magnet?

Answer 1

A magnet that is free to pivot like this is called, a compass
- The end of the magnet that points towards the North is called the North Pole, the other end is the South Pole

Question 2

What happens when you cut a magnet in half?

Answer 2

Cutting a bar magnet in half produces two weaker but still complete magnets, with a north and south pole each

Question 3

Magnetic Force is a…?

Answer 3

A Magnetic Force is a long range force just like electric force: magnets do not need to touch each other to exert force on each other.
- The basic unit of Magnetism is a magnetic dipole

Question 4

What is the SI Unit for a Magnetic Field?

Answer 4

Tesla (T)

Question 5

How do we measure a Magnetic Field?

Answer 5

A magnet creates a magnetic field everywhere around it, . We use a compass to measure the direction of a magnetic field
- We can use iron fillings to picture a magnetic a field

Question 6

What is a Magnetic Field Vector?

Answer 6

The magnetic field vector representation is useful if we want to represent the magnetic field at one particular point
- Magnetic field lines are often simpler to use

Question 7

The Magnetic Field Lines due to a Bar magnet are directed…?

Answer 7

The magnetic field lines due to a bar magnet are directed from the north pole to the south pole
- The field is stronger near the magnet and weaker further away

Question 8

Like Poles do what?

Answer 8

attract each other, and the field likes of two like charges cancel each other.

Question 9

Unlike Charges do what?

Answer 9

unlike charges repel each other

Question 10

Earth is a..?

Answer 10

Earth is a magnet, with a north and south pole

Question 11

What do magnetic field lines do around curved loops?

Answer 11

The magnetic field lines curve through the loop, around the outside and back through the loop’s centre, forming complete closed curves

Question 12

What is a solenoid?

Answer 12

A solenoid is a series of current loops placed along a common axis
- Inside the solenoid the field lines are relatively evenly spaced The field inside is NEARLY uniform

Question 13

What is the Right-Hand Rule for Straight-Current Carrying wire?

Answer 13

1. Point RIGHT thumb in the direction of current
2. Wrap your fingers around the wire to indicate a circle
3. Your fingers curl in the direction of the magnetic field

Question 14

For Straight Current-Carrying Wire what does (X) mean?

Answer 14

(X) means the Currents direction is INTO the PAGE

Question 15

For Straight Current-Carrying Wire what does (•) mean?

Answer 15

(•) means the Currents direction is OUT of the PAGE

Question 16

What is the formula to find the magnetic field for a Straight Current-Carrying Wire?

Answer 16

B = μoI/2πr

μo is a permeability constant = 1.26*10^-6 Tm/A

Question 17

What is the Formula to find the magnetic field for a Single and Multiple Loops?

Answer 17

B = μoI/2R

- For Multiple Loops = B = μoNI/2R

Question 18

What is the Formula to find the magnetic field for a Solenoids?

Answer 18

B = μoNI/L

• The greater the ratio of N turns of wire, to the length L of so the solenoid (N/L) the STRONGER the field inside
• The magnitude of the field is proportional to the current (I) in the solenoid
• The field does not depend on the radius of the solenoid

Question 19

What do Electric Fields do?

Answer 19

Electric fields exert force on charges

F = qE

Question 20

What direction do positive charges accelerate in Electric Fields?

Answer 20

positive charges accelerate in the direction of the field (because electric fields are in the perspective of a proton)

Question 21

What direction do negative charges accelerate in Electric Fields?

Answer 21

negative charges accelerate in the direction opposite of the electric field

Question 22

Magnetic Fields do what?

Answer 22

Magnetic fields exert force on particles

F = vqB

Question 23

Magnetic Forces on Moving Charges: At Rest and Parallel?

Answer 23

There is NO magnetic force on a charged particle at rest, or on a charged particle moving parallel to a magnetic field

Question 24

Magnetic Forces on Moving Charges: perpendicular to Magnetic Force?

Answer 24

If (v) is perpendicular to to the plane containing (v) and (B)
- As the angle increases between the velocity and magnetic field, the Magnetic Force increases greatest when (90°)

Question 25

What is the Right Hand Rule to Determine the Direction of Magnetic Force?

Answer 25

F = |q|vBsinα 1. Spread your fingers out so your index finger and thumb are perpendicular to each other 2. Rotate your thumb in the direction of (v) and you index finger in the direction of (B) 3. Now point you middle finger up, so it is perpendicular to your palm (it will point in the direction of v*B)

Question 26

if the Charge |q| is positive what happens?

Answer 26

if the Charge |q| is positive, F = |q|vBsinα points in the direction of (v*B)

Question 27

If the Charge |q| is negative what happens?

Answer 27

If the Charge |q| is negative, F = |q|vBsinα points in the direction opposite of (v*B)

Question 28

What is Uniform Circular Motion?

Answer 28

Uniform Circular motion is motion in a circle at a constant speed - A charged particle moving perpendicular to a uniform magnetic field, undergoes uniform circular motion

Question 29

What is Helical Motion?

Answer 29

If the charged particles velocity is not perpendicular to the uniform magnetic field, The net result is a helical path that spirals around the field lines -eg) Aurora Borealis

Question 30

What is an Electromagnetic Flowmeter?

Answer 30

Is a device that can be used to measure the blood flow in an artery - it applies a magnetic field across the artery, which separates the positive and negative ions in the blood

Question 31

A Magnetic force on a Current?

Answer 31

The magnetic force is exerted on every moving charge in the wire F = ILB or F = ILBsinα

Question 32

What are the forces between Current Loops?

Answer 32

- There is an attractive force between parallel loops with current in the same direction - There is a repulsive force between parallel loops with a current in the opposite direction

Question 33

A current Loop in a Uniform Field?

Answer 33

1. A current loop in a uniform magnetic field feels NO net force and instead experiences a TORQUE - Torque (T) = IABsinθ or T = μBsinθ μ = 1.0*10^-6

Question 34

What is an Area Vector?

Answer 34

The magnitude of the Area vector (A) is area (A) inside the loop

Question 35

What is a Magnetic Dipole Moment?

Answer 35

The Magnetic Dipole Moment is represented as a vector that points in the direction of the dipole's field. A longer vector means a STRONGER field - The magnitude of a Dipole Moment μ = IA

Question 36

The greater (wider) the parabola trajectory the...?

Answer 36

The greater the parabola trajectory the faster the velocity of the particle