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Physics > Electricity > Flashcards

Electricity Flashcards

0
Q

Resistance units

A

Ohms

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1
Q

How are voltage current and resistance related

A 
Voltage = current x resistance 
V = I x R
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2
Q

Ohms law

A

The current that flows through a conductor is directly proportional to the potential difference across its ends, provided it’s temperature remains constant

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3
Q

Q

A

Charge

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4
Q

What equation relates voltage, charge and energy

A

Voltage = energy/charge

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5
Q

Current

A

Rate of flow of charge

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6
Q

Why are metals good conductors of electricity

A

They have delocalised electrons

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7
Q

Why are non metals insulators

A

They have no delocalised charge carriers

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8
Q

I

A

Current

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9
Q

Equation that relates charge current time

A 
Current = charge/time 
I = Q/t
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10
Q

Voltage

A

Joules per coulomb

Energy per unit charge

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11
Q

Resistance

A

How difficult it is for a current to flow through a material

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12
Q

In dark conditions LDRs resistance is what, and why

A

High, because they contain few free electrons

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13
Q

What happens to the resistance in LDRs when light is shone on them

A

More electrons are freed and the resistance decreases

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14
Q

What is the resistance like in a thermistor at room temperature

A

Large, because the number of free electrons is small

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15
Q

What happens to the resistance when a thermistor is warmed

A

The resistance decreases as the number of free electrons increases

16
Q

LEDS

A

Light emitting diodes - diodes that glow when a current is flowing through them

17
Q

Current in a circuit flows from

A

The positive terminal to the negative terminal (the delocalised electrons move about in the opposite direction)

18
Q

1 coulomb contains how many electrons?

A

6.25 x 10^18

19
Q

If the voltage increases, the current

20
Q

Why is the graph of current against voltage for a filament lamp bit a straight line

A

The wire in a filament lamp gets hotter for larger currents
More kinetic energy, more particle collisions
This increases the resistance

21
Q

1 mC (milliCoulombs)

22
Q

What does a variable resistor do

A

Changes the current in a circuit by changing the resistance

23
Q

LDRs resistance in dark conditions

A

Contain few free electrons and so have a high resistance

24
Q

LDRS resistance when light is shone on them

A

More electrons are freed and resistance decreases

25
Q

Thermistors uses

A

In temperature-sensitive circuits and devices such as fire alarms and thermostats

26
Q

LDRS uses

A

In light-sensitive circuits and devices such as photographic equipment automatic lighting controls and burglar alarms

27
Q

Unit of charge

Physics (17 decks)

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