Electrostatics

Question 1

Electric Field effects on charged particle

Answer 1

• can accelerate the particle from rest
• do work on a charged particle
• moving charged particles are deflected by perpendicular e.fields
• F=qE

Question 2

magnetic effects of charged particle

Answer 2

• moving charged particles traverse in a circle thru perpendicular magnetic fields
• do not accelerate charged particle from rest
• do no work on a charged particle
• depends on speed of particle and magnitude of charge

Question 3

When voltage is applied to a wire with no net charge, what will the resulting net charge be?

Answer 3

• current will make electrons flow into and out of the wire
  
  • on average the number of electrons entering wire = # exiting - thus net charge is zero

Question 4

current

Answer 4

traditionally defined as flowing positvie charges from higher voltage to lower voltage

Question 5

electric field

Answer 5

• region of space where a charged particle would feel an electrostatic force if it were placed there - referred to as a test charge (q’)
• test charges generally considered to be positive
  
  • thus field moves away from positive charges and towards negative charges
• denoted as E
• units of N/coulomb
• vector quantity

Question 6

electric field equation

Answer 6

E=F/q’

electric force F acting on a test charge divded by the charge of the test charge

Question 7

electric field lines

Answer 7

point in direction of how a positive charge moves

• the closer the lines are the stronger the field is

Question 8

equipotential lines

Answer 8

• lines in electric field that a test charge would experience the same force and have the same potential to move
• connects all pts within an electric field sharing the same potential
• no work done by electric field if test charge moves position within same equipoential line

Question 9

when is work done a test charge by an electrical field?

Answer 9

• when the field has a tangent component to the equipotential surface
  
  • equipotential lines and electric field lines are perpendicular

Question 10

what is the potential change when a test charge moves in the direction of a field line?

Answer 10

• the charge moves from higher potential to lower potential

Question 11

electrical potential energy

Answer 11

• increases when like charges are brought together and vice versa
• decrease when opposite charges are brought together and vice versa
• PEq=Kq₁q₂((1/r_f))-(1/r_i))

Question 12

electrical potential difference

Answer 12

• difference in electrical potential energy from starting position to ending position of a moving charge divided by the charge of the particle
• J/coulomb = a VoltP
• PE_q=qV
• absolute potential is arrbitrary point assigned a zero voltage

Question 13

dielectric constant

Answer 13

• ratio of electrical forces between to charges when they are in a vacuum vs when they are in a medium
• increases with increasing polarity of the medium - the more interactions the medium can undergo, the more disruptive it can be to interacting charges
• Fmedium = Fvacuum/K where K is the dielectric constant of the medium
• F=Kq1q2/Kr²

Question 14

electric dipole

Answer 14

• P=qL
• occurs when two charges of opposite signs are separated from eachother by some distance L
• q is product of the charge

Question 15

magnetic field

Answer 15

• moving charged particle can create
• depends on speed of particle and magnitude of charge on particle
• can exert a force on any other charge moving through the field
• can be linear or radial depending on charge’s movement
• vector - magnitude and direction
• B (N*s/C*m) - Tesla = N/A*m - because one Ampere is C/s
• always form closed loops - move from north pole to south pole

Question 16

Lorentz Force

Answer 16

• force exerted on a moving particle by a magnetic field
• F_magnetic=qvBsinσ
• force is greatest when velocity of charged particle is at right angles with magnetic field - lowest when parallel

Question 17

right hand rule for magnetic fields

Answer 17

• thumb for velocity of particle
• fingers for B
• palm for force of magnetic field
• based on motion of positive particle

Question 18

solenoid

Answer 18

• should be at least 4xs as long as its radius
• passing a current thru the coil results in magnetic field - depends on magnitude of current and dimensions of solenoid (number of turns in solenoid)