Electricity / Magnetisim (7-9)

Question 1

ELECTRICITY

Question 2

Electric charge (FS)

Answer 2

• F = k(q1q2)/d^2

Question 3

Electric fields (FS)

Uniform electrical fields

Electrical field of a single point of charge

Electrical field between parallel plates (FS)

Answer 3

• F = Eq
  • W = qEd
  • E = k(Q/r^2)
  • E = deltaV/d

Question 4

Electrical potential energy

Answer 4

• Pe = qV
  
  • Pe = 1/2CV^2

Question 5

Voltage

Electrical potential (VOLTAGE) due to a positive or negative charge (FS)

Answer 5

• deltaV = W/q
  
  • W = q*deltaV
  • V = k*(Q/r)

Question 6

Capacitance (FS)
(FS)

Answer 6

• Q = CV
  
  • C = funny(e )*(A/d)

Question 7

Energy density

- If there is dielectric

Answer 7

• 1/2funny(e )E^2
  • 1/2Kfunny(e )*E^2

Question 8

Electric current (FS)

Answer 8

• Q = It

Question 9

Ohm’s law (FS)

Answer 9

• V = IR

Question 9

Resistance (FS)
(FS)

Answer 9

• R = (roe*L)/Area
  
  • Roe(T) = roe(0)[1+a(T-T(0)]

Question 10

Alternating current

Answer 10

• I = V/R
  
  • I = V0/Rsinfunny(w)*t
  • Average power = (V0*I0)/2
  • V(rms) = V(peak)/sqrt2
  • I(rms) = I(peak)/sqrt2

Question 10

Power in a circuit (FS)

Answer 10

• P = IV
  
  • P = V^2/R
  • P = I^2*R

Question 11

Series circuits

Parallel circuits

Answer 11

Series
- I is the same for all resistors
- Vtotal = V1 + V2 + V3
- Re = R1 + R2 + R3

Parallel
- Vtotal = V1 + V2 + V3
- Itotal = I1 + I2 + I3
- 1/Re = 1/R1 + 1/R2 + 1/R3

Question 12

MAGNETISIM

Question 12

Magnetic field from a current carrying conductor (FS)

Answer 12

• B = (mew0*I)/2pir
  ○ Where mew0 is permeability of free space

Question 13

Force on a current carrying wire (FS)

Answer 13

• F = BiLsinx
  ○ Where B is magnetic field
  ○ Where I is current
  ○ Where L is length of wire in the field
  ○ Where x is the angle between the wire and the field

Question 14

Force between 2 parallel wires (FS)

Answer 14

• F = (mew0I1I2*L)/2pix
  ○ Where L is length of the wires
  ○ Where x is the distance between the wire

Question 15

Solenoids and electromagnets (FS)

Answer 15

• B = (mew0NI)/L
  ○ Where N is the number of windings
  ○ Where L is the length of the electromagnet not the length of the wire

Question 16

Charges in magnetic fields

Answer 16

• F = qvBsinx
  ○ Where v is the velocity of q

Question 17

Circular motion by a charged particle in a magnetic field (FS)

Velocity selector
- v = E/B

Answer 17

• r = mv/qB
• v = E/B

Question 17

Mass spectrometer
(remember special case)

Answer 17

• M = (qBB’*r)/E
  ○ Where B and B’ are different magnetic fields

○ These are almost always the same (meaning you only use it once not twice)

Question 18

Magnetic flux (FS)

Answer 18

• Phi = BAcosx
  ○ Where x is the angle between the magnetic field and the normal of the loop of wire

Question 19

Faradays law (FS)

Answer 19

• V = -N*(detla(phi)/delta(t))
  ○ Where phi is magentic flux
  ○ Where N is number of loops

Question 20

AC voltage

RMS voltage (FS)

Answer 20

• Phi = BAcosx
• Vpeak/sqrt2

Question 21

Power loss

Answer 21

- P = I^2R ○ Where R is resistance of transmission line

Question 22

Transformers

Answer 22

- Delta phi/delta t ○ Where phi is primary voltage ○ Where t is number of primary turns