Potential Difference Flashcards

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1
Q

what does a cell actually produce

A

an electromotive force

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2
Q

what does an electromotive force create

A

a potential difference in a circuit

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3
Q

what does this potential difference in the circuit do

A
  • the charge carriers in the circuit components and connecting wires experience a force
  • causing the charges to move around the circuit
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4
Q

why does the presence of potential difference directly lead to there being power in the circuit

A
  • because the potential difference is doing work on the charges
  • and if its doing work energy is being transferred
  • as this is happening as time passes, the rate of work done or energy transferred can be calculated
  • which is what power is
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5
Q

there is a reservoir of water attached to a paddle wheel in a cylinder which has a pipe going into a sink. the reservoir is above the paddle wheel and a tap is in between them. what is different between the reservoir and the pipe connecting the pieces

A
  • the pressure difference in the reservoir is much larger than in the pipes
  • as the reservoir is holding the weight of water
  • whereas the pipes arent
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6
Q

what happens when the tap is opened and what is it caused by

A
  • the water flows down the pipe and turns the paddle wheel

- this is because of the pressure difference

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7
Q

what is the energy transfer taking place when the tap is opened

A
  • the gravitational potential energy of the water is being transferred to its kinetic energy stores as it flows down
  • then that is transferred to the kinetic energy stores of the paddle
  • causing it to rotate
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8
Q

in an actual circuit, what is happening in the cell which cause it to produce an electromotive force

A
  • a chemical reaction

- this is what gives rise to the electrical potential difference across the cell terminals

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9
Q

if there is a switch in the circuit which is open, would the electrons still feel a force from the electrical potential difference created by the cell

A
  • yes
  • because its existence exerts a force on the electrons either way
  • its just that the electrons arent moving as the circuit isnt complete
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10
Q

what does it mean if the electrons arent moving even though a force is being exerted on them

A
  • work isnt being done on the electrons
  • as work = force x distance and there is no distance being traveled
  • which correctly implies that there is no power in the circuit
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11
Q

what happens when the switch is closed

A
  • the electrons experiencing the force begin to move around the circuit
  • now that they are moving work is being done on them
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12
Q

why does the temperature of the filament lamp begin to rise in terms of energy transfers

A
  • the chemical potential energy stored in the cell is converted to vibrational kinetic energy of the atoms in the filament of the lamp
  • this vibration releases thermal energy
  • causing the temperature to rise
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13
Q

what is the basis of the definition of potential difference

A

that electrical energy in a circuit can be converted into other types of energies

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14
Q

what are the energy transfers for light to be produced in a circuit and for a motor to work

A
  • electrical energy is transferred to the kinetic and thermal energy stores of a filament lamp, producing light
  • and electrical energy is powering a motor by transferring its energy to its kinetic energy stores
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15
Q

using the basis of the definition of p.d. what would the potential difference between two points in a circuit be called

A
  • the electrical energy per unit charge

- converted into other forms of energy

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16
Q

what word equation can be written from that deduction for p.d.

A

p.d. = electrical energy being converted into other forms / charge passing

17
Q

what would electrical energy being converted into other forms and charge passing be simplified to

A
  • work done, W (as energy transferred = it)

- and charge, Q

18
Q

what equation would then be derived from those 3 variables

A
  • V = W / Q

- basically the same as E = QV

19
Q

what would the unit for this p.d. be and what is it called

A
  • it would be JC^-1

- also called the volt