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Level 163

Magnetic Force & Field


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magnet
a body that can attract certain substances, such as iron or steel, as a result of a magnetic field
Magnitude of a Magnetic Field (B)
Also known as magnetic field strength, magnetic field intensity, magnetic flux density. Ratio of magnetic force on a current carrying conductor to the product of the current and length of wire and sine of…
Right Hand Rule
Fingers - Direction of magnetic field (B)
First: Into the page
Notation for in and out of the plane
Magnetic flux density equation
B = F / IL sin theta
units of magnetic flux density (B)
tesla = T = N A-1 m-1
F = B Q V sin theta
force on a charged particle moving in a magnetic field
field direction, direction of velocity, sign of charge
how may the direction of the force on a charged particle moving in a magnetic field be reversed? by reversing:
magnetic force
a the force of a magnet
r = m v / B Q = p / B Q
Formulae for radius, relating the force on a charged particle moving in a magnetic field
Law of Conservation of charge
the total charge of a closed system is constant
conductor
A material that allows heat and electricity to pass through it.
insulator
A material that blocks the flow of energy.
Coulomb's Law
… the two charges. (F=k q1 q2 / r^2)
Electric Field Strength(E)
Electric force per positive unit test charge (E=f/q)
Radial Field
Field that extends radially (like the electric field around a point charge or the gravitational field around a planet)
Electric Potential(V)
Work done per unit charge moving a small positive test charge in from infinity to a point in an electric field. (V=W/q) (V=kq/r)
Electric Potential Energy (Ep)/(Ee)
Energy that a charge has due to its position in an electric field
Electric Potential Difference(ΔV)
Electric potential difference per unit charge between two points in an electric field(ΔV = ΔEe/q OR ΔV = W/q)
Electronvolt (eV)
Energy gained by an electron moving through an electric potential difference of one volt. (Work done moving an electron through an electric potential difference of one volt) (1 eV = 1.6 * 10^-19 J)
Electric Current(I)
Current is defined in terms of the force per unit length between parallel current-carrying conductors (One ampere of current is the amount of current in each of two infinitely long straight wires one meter a…
Resistance(R)
Ratio of potential difference applied to a device to the current through the device (R=V/I)
Resistor
Device with a constant resistance (Ohmic device) over a wide range of potential differences
Ohm's Law
for ohmic resistors: current is proportional to voltage at constant temperature. (V = RI)
Ohmic Device
One whose resistance remains constant over a wide range of potential differences (resistor)
Non-Ohmic Device
One whose resistance does not remain constant over a wide range of potential differences (eg - filament lamp)
Electromotive Force (emf) (ε)
Total energy difference per unit charge around a circuit (total energy per unit charge made available by the chemical reaction in the battery) (ε=ΔEe/q OR ε=W/q)
Internal Resistance (r)
Resistance inside a battery that causes the battery's terminal potential difference to be less than its emf (Internal resistance in a meter causes it not to act as an ideal meter)
Ideal Ammeter
One with zero internal resistance - must be placed in series
Ideal Voltmeter
One with infinite internal resistance - must be placed in parallel
Potential Divider
Two resistors placed in series that divide up the battery's potential difference(R1/R2 = V1/V2)
Light-Dependent Resistor (LDR)
Sensor whose resistance depends on amount of light shining on its surface - increase in light causes a decrease in ressitance
Negative Temperature Coefficient (NTC) Thermistor
Sensor whose resistance depends on its temperature - increase in temperature causes decrease in ressitance
Strain Gauge
Sensor whose output voltage depends on any small extension or compression that occurs which results in a change of length
Magnitude of a Magnetic Field (Magnetic field strength, magnetic field intensity, magnetic flux density) (B)
Ratio of magnetic force on a current carrying conductor to the product of the current and length of wire and sine of the angle between the current and the magnetic field (…
direction of a magnetic field
The direction of a magnetic field at a given location is defined as the direction a compass needle would point if placed at that location.