P2.3 (Currents) Flashcards

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1
Q

What is static electricity?

A

Static electricity is a stationary electrical charge

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2
Q

What are the rules of attraction?

A

If the charges are the same, they REPEL
If the charges are opposite they ATTRACT
If one is charged and one is not they ATTRACT

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3
Q

If a substance loses electrons, what is it’s charge?

A

POSITIVE

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4
Q

Does a substance gain or lose electrons in order to become negatively charged?

A

GAIN

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5
Q

How do you work out power?

A

Power = voltage x current

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6
Q

How do you work out voltage?

A

Voltage = power / current

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7
Q

What is current measured in?
What is voltage (potential difference) measured in?
What is power measured in?

A

A (amps)
V (volts)
W (watts)

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8
Q

What is the power of a 5 A 1.5 V lamp?

A

5 x 1.5 = 7.5W

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9
Q

What is the purpose of fuses?

A

The fuse keeps the circuit safe as it burns out when the current increases past the current the fuse can handle.

It does this by being a thinner wire than the rest of the circuit and so when the current increases, the resistance in the thin wire becomes too much and the wire burns out.

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10
Q

Is the current equal in all parts of the circuit in a series or parallel circuit?

A

A SERIES CIRCUIT

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11
Q

How is the current distributed in a parallel circuit?

A

It splits between branches

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12
Q

What’s Kirchoff’s second law?

A

Sum of PD’s in a cell = sum of PD’s in each branch

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13
Q

How is the potential difference distributed in parallel and series circuits?

A

In a parallel circuit the potential difference is the same in every component
In a series circuit the potential difference splits between components.

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14
Q

SERIES SYMBOLS

A

LOOK IN BOOK

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15
Q

What is the equation for resistance distribution in a series circuit?

A

Rt = R1 + R2

in book diagram

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16
Q

What is the equation for resistance distribution in a parallel circuit?

A

1/Rt = 1/R1 + 1/R2

Rt is less than either resistance

17
Q

Why does static electricity only work with insulators not conductors?

A

In conductors, the electrons are able to flow away instead of staying static

18
Q

What is potential difference?

A

The energy given to/by electrons

19
Q

What would the resistance in a circuit do as the temperature increased?

A

decrease

20
Q

In an LDR, does the resistance rise or fall with the intensity of the light?

A

FALLS

21
Q

How do you work out charge?

A

Charge = current x time

C = A x S

22
Q

How do you work out work done?

A

Work done = potential difference x charge

23
Q

Does the resistance increase or decrease through a thin wire and why?

A

The resistance will increase as there is less space for the electrons to flow so they bump into each other and lose energy causing the wire to heat up.

24
Q

What is resistance?

A

A measure of how much obstruction there is to an electrical flow.

25
Q

If you get a shock after touching a metal object, are you a conductor or insulator?

A

Insulator

26
Q

What is the relationship between current and voltage?

A

Current and voltage are always directly proportional to each other at constant temperature

27
Q

What does an IV graph show?

A

For a particular component, an I-V graph shows what current will flow across the component when a potential difference is applied

28
Q

What gives wires resistance?

A

Electrons moving through the wire collide with fixed ions and lose energy, in thinner wires collision is more likely

29
Q

Two resisters of 100 Ω and 50 Ω are connected in series. The voltage drop across the two resisters is 15V. What is the current running through the circuit?

A

0.1 A

100 + 50 = 150

15 /150 = 0.1