Physics: Magnetism And Circuits Flashcards
Magnetic field
A charged particle that is moving and experienced a push or force is magnetic field
Units of Magnetic field: Tesla
- B= N • s/ m • C —> F= C • B • m/s
- F= C • B • m/s —> F(B)= q • B • v • sin θ
Charged Particles in a magnetic field
Experience a Force: Lorentz force
- F= q • v • B • sin θ
Right hand rule
Made for positively charged particles
Thumb is the direction of Velocity
Fingers are direction of field
Palm is direction of Force
Motion completely inside Magnetic Field
Force changes direction as velocity changes direction.
A charged particle inside of a magnetic field will move to become a perfect circle.
Centripetal force provided by magnetic field force
- Fc= q•v•B sin θ
Centripetal force
Causes an object to turn in a circle
- formula: Fc= mv²/R
Current
Flow of positive charges
- opposite of electrons ((-) -> (+))
- current (i)= Δq/Δt ( in amperes)
- ampere= C/s
Wires with current in magnetic fields
Fi= i•l•B•sinθ
Right hand Rule
- Thumb= direction of force
- Straight Fingers= direction of current
- Bent fingers=direction of magnetic field
3 types of Magnetism
Paramagnetism
- unpaired electrons
- attracted to external magnetic fields
Diamagnetism
- only paired electrons
- repelled by external magnetic fields.
Ferromagnetism
- permanent magnets
Electric circuits
Circuit components
- voltage supply
- wires
- resistors
- capacitors
Cell voltage
- V= electromotive force of battery - (internal resistance) • ( current)
Ohm’s Law
Voltage is proportional to current
- V= iR
Power in circuits
- P= iV
Resistivity
Impeded the flow of e-
Based on:
- material
- Length of resistor
- Area of resistor
R ∝ Length
R inversely proportional to Area
Formula for Resistance
Resistance of a resistor: R = (Resistivity * L)/ Area
- Measured in Ohms (Ω) • m
Resistance changes with temperature. Higher temperature means higher resistance.
Kirchhoff’s Current Law
At a junction current in= current out
- ∑i in = ∑i out
Conservation of charge
- i1 + i2= i3
Kirchoff’s Voltage Law
Around a circuit, sum of voltage supply= sum of voltage drops
- ∑Vsupply = ∑V drops
Resistor in a series
Current is the same
Total resistance= R1 + R2 + R3…
Voltage drops across each
