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physics > Topic 3- Electricity > Flashcards

Topic 3- Electricity Flashcards

1
Q

What is charge?

A

Property of a particle, that can be positive or negative.

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2
Q

What is charge measured in?

A

Coulombs, C

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3
Q

What is the equation for current?

A

I = Q/t
Or
Current= Change in charge / Change in Time

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4
Q

What is the charge of an electron?

A

1.6x10^-19 coulombs

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5
Q

What is one coloumb defined as?

A

The amount of charge transferred by a current of 1 amp in one second.

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6
Q

What is drift velocity?

A

The average velocity of an electron in the direction of current.

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7
Q

The prefix ‘G’ means?

A

Giga (x1,000,000,000 or 10^9)

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8
Q

The prefix ‘k’ means?

A

Kilo ( x 1000 or 10^3 )

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9
Q

The prefix ‘m’ means?

A

Milli ( ÷ 1000 or 10^-3)

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10
Q

The prefix ‘μ’ means?

A

Micro (÷ 1,000,000 or 10^-6)

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11
Q

The prefix ‘n’ means?

A

Nano (÷1,000,000,000 or 10^-9)

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12
Q

The prefix ‘p’ means?

A

Pico (÷1,000,000,000,000 or 10^-12)

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13
Q

What is voltage?

A

A measure of the amount of energy a component transfers per unit charge.

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14
Q

What is the difference between electromotive force and potential difference?

A

E.M.F Supplies energy

P.D Uses energy

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15
Q

Sum of p.d and e.m.f is always….

A

Equal

(due to the conservation of energy)

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16
Q

What is an electron Volt?

A

1.6x10^-19
Charge of electron when passing through a p.d of one volt

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17
Q

What causes resistance?

A

Charge carriers (ie. electrons) colliding with lattice ions and being scattered.

18
Q

Equation for resistance?

A

resistance = PD/current

19
Q

What is Ohm’s Law?

A

Current through an (ohmic) conductor is directly proportional to the potential difference across it.

Providing temperature remains constant.

20
Q

What does the IV graph look like for an ohmic conductor?

A

Positive linear graph

21
Q

What is resistivity?

A

Property of a material, measuring its resisting power.

22
Q

Equation for resistivity?

A

R=pl/A

23
Q

How does increasing the cross-sectional area of a conductor affect its resistance?

A

The larger the cross-sectional area of a conductor, the lower its resistance, assuming all other factors remain the same.

24
Q

How does it increasing the length of a conductor affect resistance?

A

The longer the conductor, the higher the resistance. Assuming all other factors stay the same.

25
Q

What equation links the number of charge carriers in a metal, along with drift velocity, to the current flow?

A

I=nqvA

26
Q

What is a semiconductor?

A

A component that can change its resistance based on external factors.

27
Q

Give two examples of semi conductors and what they’re sensitive too.

A
  1. LDRs are sensitive to light
  2. Thermistors are sensitive to temperature
28
Q

Describe how the resistance of a thermistor changes as the temp decreases

A

As the temp decreases, the resistance increases.

29
Q

Describe how the resistance of an LDR changes as the light intensity increases.

A

As light intensity increases, resistance decreases.

30
Q

How many loops can current take in a series circuit?

A

One

31
Q

Does current differ at different points around a series circuit?

A

No

32
Q

Does current differ at different points around a parallel circuit?

A

*Current splits at each point that it encounters a junction
*It splits in inverse proportion to the resistance along each path.
*The sum of all the currents on each path will add up to the original current from the battery.

This is due to the conservation of charge.

33
Q

In parallel branches, what must the sum on voltages add up to?

A

They must be equal.

34
Q

What rules does the conservation of energy cover in circuits?

A

*e.m.fs around a series circuit will add up, accounting for their directions.

*The sun of p.ds across components in a series circuit will be equal to the sum of e.m.fs

*In any parallel branches of a circuit, the sum of the voltages must be equal.

35
Q

Resistors in series- derivation

A

Across resistors:
Vtot = V1 + V2+V3. (CoE)

As V=IR, and current is the same for all components around a circuit.
So:
IRtot= IR1+ IR2 +IR3. (CoC)
Rtot=R1+ R2 +R3

36
Q

What is current?

A

Rate of flow of charge, per unit charge.

37
Q

What’s the principle of charge conservation?

A

States that the total electric charge in a closed loop does not change.

38
Q

What is Kirchoff’s first law?

A

The total current flowing into a junction is equal to the current flowing out of that junction.

39
Q

Kirchoffs Second Law

A

The sum of the e.m.f.s is equal to the sum of the p.d.s in a closed loop (a form of conservation of energy).

40
Q

What is Power defined as

A

The rate of energy transferred.
P=VI

41
Q

What is internal resistance?

A

Caused by electrons colliding with atoms inside a battery, so energy is lost before electrons leave the battery.

physics (7 decks)

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