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Physics 30 > Electric Forces and Fields > Flashcards

Electric Forces and Fields Flashcards

1
Q

What is electric charge? What unit is it measured in?

A

Electric charge is a physical property of matter that causes it(matter) to experience a force when placed in an electric field? Electric charge(q) is measured in units of Coulombs(C)

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2
Q

What is an alpha particle?

A

An alpha particle is a Helium particle without electrons
Has a charge of +2

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3
Q

Objects with an equal number of protons and electrons are ___________

A

Neutral (q=0)
Note: Protons and electrons offset each other(NET charge is 0). Objects still have charges in them.

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4
Q

The charge of an object is ___________(1). This means that it must come in a ______________(2) of a base unit called the ________________(3) where e = __________________(4)

A

(1) Quantized
(2) Whole number multiple
(3) Elementary charge e
(4) 1.60 x 10 ^-19 C

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5
Q

The Law of Charges states that ______________________

A

Like charges repel, and opposite charges attract

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6
Q

What is Conservation of Charge, adn what circumstances must be met for this to hold true? What key physics principle refers to conservation of charge?

A

When objects in a system interact, the net charge before (sigma qb) the interaction is equal to the net charge after the interaction (sigma qa)
- Only valid in a system that is closed and isolated
-Key physics principle 7

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7
Q

What is inertia? What is inertia dependant on?

A

Inertia is an object’s tendency to remain in the state it is in(les responsive to external forces). Inertia is dependant on mass(higher mass = higher inertia).

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8
Q

Protons have a mass that is __________(1) than that of an electron. Because of their lower inertia, electrons are far ____________(2) to electrical influences than protons. Electrons ____________(3) around an object, while protons are _____________________(4).

A

(1) Larger
(2) More responsive
(3) Can move
(4) Fixed in place

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9
Q

What is a conductor?

A

A conductor is a material in which electrons can easily move around(ie. metals).

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10
Q

What is an insulator?

A

An insulator is a material where there is greater resitance to the movement of electrons, and therefore the electrons cannot move around as easily(ie. glass, plastic).

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11
Q

In an insulator, electrons tend to be in ______________ to one another.

A

Close proximity (because they can’t move around/away from each other)

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12
Q

Electrons ___________________________ of symmetrical conductors.

A

evenly distribute along the surface of

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13
Q

What is electrical conductivity?

A

Electrical conductivity is a material property that describes how tightly bound electrons are to the protons in the nucleus

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14
Q

What are the four methods of charging objects?

A
  1. Charging by friction
  2. Charging by conduction
  3. Charging by induction
  4. Charging by induction through grounding
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15
Q

What is charging by friction?

A

The transfer of electrons from one object to another but rubbing them together. The object with the higher EC will transfer electrons to the other object. Net charge of the system before and after is the same.

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16
Q

What does High EC mean?

A

ELectrons are more loosely bound to the nucleus and can more easily be transferred to a different object

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17
Q

What does low EC mean?

A

Electrons are more tightly bound to the nucleus adn are less likely to be transferred to a different object.

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18
Q

What is charging by conduction?

A

The transfer of electrons from one object to another as a result of direct contact without the requirement of rubbing the objects together. Electrical conductivity does not matter in conduction.

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19
Q

What happens in conductors with identical surface area?

A

The electrons will repel and evenly distribute over the surface of both conductors.

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20
Q

What happens in conductors with different surface areas?

A

The object with the larger surface area will carry more electrons

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21
Q

What is charging by induction?

A

Charging by induction occurs when a charged object polarizes a neutral conductor, without contacting the objects together. A conductor is polarized when one side has a negative charge, and the other side has a positive charge. Net charge is still zero.

22
Q

What is charging by inductions through grounding?

A

When a polarized conductor is connected to the ground, electrons can either be repelled into the ground(leaving the conductor with a positive charge) or attracted into the conductor(giving the conductor a negative charge)

23
Q

What does Coulomb’s law describe?

A

Coulombs law describes the magnitude of the electrostatic force between two charged objects

24
Q

Coulomb’s Law is identical in format to that of ________________.

A

Newton’s Universal Law of Gravitation

25
Q

Coloumb’s constant was determined through ________________.

A

An adaptation of Cavendish’s Torsion Balance Experiment where the masses were charged.

26
Q

Draw a diagram of Cavendish’s torsion balance experiment apparatus.

A

Refer to notes

27
Q

What is an electric field?

A

A region of influence surrounding an object with charge.

28
Q

How is the direction of an electric field determined?

A
  • Placing a small positive test charge in the electric field and then identifying the direction of the electrostatic force acting on the test charge.

Has to be a small charge(not necessarily a small mass)or it would have a stronger field of influence than the source charge

29
Q

What is a test charge?

A

The object which is experiencing influence/force in the electric field

30
Q

Out of the two equations for calculating electric field strength, identify which equation can be used for a test charge and a test charge.

A

Refer to notes

31
Q

What is electric potential energy?

A
  • E(p)
  • Energy of a charges object due to its position in an electric field
  • The work done by an applied force to move a charge in the electric field at a constant velocity can be determined using the work-energy theorem

W(A) = E(p)

32
Q

When work is done against the electric field, the objects E(p) ____________(1). When work is done by the electric field, the objects E(p) ____________(2). When the objects motion is perpendicular to the electric field, the objects E(p) __________(3).

A

(1) Increases
(2) decreases
(3) remains the same

33
Q

What is electric potential difference?

A
  • (delta) V
  • A measure of the work required to move 1.0 C of charge a specific distance in an electric field
  • Measured in units of volts(V)
34
Q

(delta)V is positive when ______________(1). (delta)V is negative when ______________(2). (delta)V is zero when ______________(3).

A

(1) moving against the electric field
(2) moving with the electric field
(3) perpendicular to the electric field

35
Q

What is a parallel plate?

A

When a battery is hooked up to two metalc plates, the battery will do work to build a negative charge on one plate and leave the opposite plate with a positive charge. This set up produces a uniform electric field in the region between the plates.

The electric field intensity between the plates is calculated by E = v/d

36
Q

To determine the speed of an ion when dealing with parallel plates, ________________(1) can be used.

A

(1) Conservation of energy

37
Q

Describe the Millikan Oil Drop Experiment.

A

An atomizer sprays charged oil droplets into the electric field. Voltage is adjusted until there is no motion of the drops in the vertical direction.

38
Q

Draw a diagram of the Millikan Oil Drop Experiment.

A

Refer to notes

39
Q

Draw an FBD and determine an equation that can be used for Millikan’s Oil Drop Experiment

A

Refer to notes

40
Q

What were the conclusions from Millikan’s Oil Drop Experiment?

A
  • the magnitude of the charge for each oil drop can be calculated although there is a large variation in both the charge and mass of each drop
  • Robert Millikan determined that the charge on each drop is a whole number multiple of a base unit of charge
  • This experiment confirmed that charge on an object is quantized and lead to calculating the value of the elementary charge
41
Q

What is electric current?

A

The amount of charge moving past a specific point in a conductor over a certain time interval. Measured in Amps

42
Q

What is resistance?

A
  • Resistance limits the current that flows from a. specific potential difference
  • Exists even in good conductors
  • Measured in Ohms(horseshoe)
43
Q

What is resistance dependant on?

A
  • The length of the conductor(L): resistance varies directly with L
  • The cross-sectional area of the conductor(A): Resistance varies inversely with A
    -The temperature of the conductor: Resistance increases as temperature increases
  • The nature of the material: Dependant on the material resistivity(p)m the material resistivity is temperature dependent.
44
Q

What is Ohm’s law?

A

The potential difference(amount of electric potential lost) across a wire is calculated by

(delta)V = IR

45
Q

What is electric power(P)?

A

The rate at which electric potential energy is dissipated by a resistor.

The rate at which electrical energy is transferred

46
Q

What are the two formulas related to electric power?

A

Refer to notes

47
Q

What is the formula for resistance?

A

Refer to notes

48
Q

What is conventional current(I)?

A

Charge moves from positive terminal(area of “excess” charge) to the negative terminal(area of “deficit” charge) of a battery

PROTONS “move” from positive to negative terminal of a batter.

49
Q

What is electron flow(e-)?

A

ELECTRONS move from negative to positive terminal of a battery

50
Q

On the symbol for a battery, the shorter length is the _____________(1) side. The longer length is the _______________(2) side.

A

(1) negative
(2) Positive

Physics 30 (8 decks)

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