Flashcards in Chapter 24 Deck (36):
What is a Magnet?
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
What happens when you cut a magnet in half?
Cutting a bar magnet in half produces two weaker but still complete magnets, with a north and south pole each
Magnetic Force is a...?
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
What is the SI Unit for a Magnetic Field?
How do we measure a Magnetic Field?
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
What is a Magnetic Field Vector?
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
The Magnetic Field Lines due to a Bar magnet are directed...?
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
Like Poles do what?
attract each other, and the field likes of two like charges cancel each other.
Unlike Charges do what?
unlike charges repel each other
Earth is a..?
Earth is a magnet, with a north and south pole
What do magnetic field lines do around curved loops?
The magnetic field lines curve through the loop, around the outside and back through the loop's centre, forming complete closed curves
What is a solenoid?
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
What is the Right-Hand Rule for Straight-Current Carrying wire?
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
For Straight Current-Carrying Wire what does (X) mean?
(X) means the Currents direction is INTO the PAGE
For Straight Current-Carrying Wire what does (•) mean?
(•) means the Currents direction is OUT of the PAGE
What is the formula to find the magnetic field for a Straight Current-Carrying Wire?
B = μoI/2πr
μo is a permeability constant = 1.26*10^-6 Tm/A
What is the Formula to find the magnetic field for a Single and Multiple Loops?
B = μoI/2R
- For Multiple Loops = B = μoNI/2R
What is the Formula to find the magnetic field for a Solenoids?
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
What do Electric Fields do?
Electric fields exert force on charges
F = qE
What direction do positive charges accelerate in Electric Fields?
positive charges accelerate in the direction of the field (because electric fields are in the perspective of a proton)
What direction do negative charges accelerate in Electric Fields?
negative charges accelerate in the direction opposite of the electric field
Magnetic Fields do what?
Magnetic fields exert force on particles
F = vqB
Magnetic Forces on Moving Charges: At Rest and Parallel?
There is NO magnetic force on a charged particle at rest, or on a charged particle moving parallel to a magnetic field
Magnetic Forces on Moving Charges: perpendicular to Magnetic Force?
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°)
What is the Right Hand Rule to Determine the Direction of Magnetic Force?
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)
if the Charge |q| is positive what happens?
if the Charge |q| is positive, F = |q|vBsinα points in the direction of (v*B)
If the Charge |q| is negative what happens?
If the Charge |q| is negative, F = |q|vBsinα points in the direction opposite of (v*B)
What is Uniform Circular Motion?
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
What is Helical Motion?
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
What is an Electromagnetic Flowmeter?
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
A Magnetic force on a Current?
The magnetic force is exerted on every moving charge in the wire
F = ILB or F = ILBsinα
What are the forces between Current Loops?
- 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
A current Loop in a Uniform Field?
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
What is an Area Vector?
The magnitude of the Area vector (A) is area (A) inside the loop
What is a Magnetic Dipole Moment?
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