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Physics A Level > Electricity U1.9-1.2 > Flashcards

Electricity U1.9-1.2 Flashcards

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1
Q

What is the definition of charge

A

One coulomb of charge passes a point in a circuit each second if a current of one amp flows

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2
Q

What is the definition of current

A

Rate of flow of charge

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3
Q

What direction is the flow of current

A

Current flows from positive to negative

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4
Q

What direction do electrons flow

A

From negative to positive

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5
Q

How does current act in parallel to series

A

Current is the same everywhere in a series circuit
Current splits across branches in a parallel circuit

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6
Q

What is the definition of Potential Difference / Voltage

A

The p.d between two points in a circuit is the electrical energy changed into other forms for each coulomb of charge which flows between the points.

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7
Q

What happens if the p.d. Between two points in a circuit is equal to 0V

A

Then no current flows between those two points

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8
Q

How does voltage act in parallel circuits compared to series

A

Current splits in series circuits where as it is the same across each branch in a parallel circuit

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9
Q

What is the definition of resistance

A

Resistance is the ratio of voltage to current

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10
Q

What is resistance the opposition of

A

Current flow

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11
Q

When is resistance caused

A

When the free electrons collide with the atoms of a conductor

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12
Q

How do you calculate the total resistance of resistors in a series circuit

A

R1 + R2 + R3….

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13
Q

How do you calculate the total resistance of resistors in a parallel circuit

A

1/Rt = 1/R1 + 1/R2 + 1/R3…..

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14
Q

What is the definition of power

A

Rate of change of energy

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15
Q

What are the three equations for power

A

P=VI
P= I^2 R
P=V^2/R

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16
Q

What is ohms law

A

A conductor held at a constant temperature obeys ohms law is the p.d. Across it is directly proportional to the current flowing through it.

If it obeys it it is said to have ohmic behaviour

17
Q

What is a super conductor

A

A super conductor is a material with an electrical resistance which drops to zero below a certain temperature, which is known as the transition temperature.

18
Q

What is a transition temperature

A

This is the temperature below which the material becomes superconducting

19
Q

Why are superconductors useful

A

They can carry large amounts of electrical current for long periods of time without loosing energy as heat.

20
Q

What is the definition of resistivity

A

Resistivity is numerically equal to the resistance of a material of unit length and unit cross sectional area

21
Q

What is the equation for resistivity

A

p=RA/l
Resistivity = Resistance x Area / Length

22
Q

What is resistivity measured in

A

Ohm meters

23
Q

What is the difference between resistance and resistivity

A

Resistance is a property of a particular conductor

Resistivity is a property which has a characteristic value for a given material

24
Q

What is the definition of emf

A

The emf of a source is the amount of energy converted into electrical energy for each coulomb of charge passing through a source

25
Q

What is the equation for emf

A

EMF = energy converted / charge

26
Q

What is internal resistance

A

Sources such as batteries will have some opposition to the current which passes through them.

27
Q

What are the equations for internal resistance

A

E=V+Ir
E=IR+Ir
E=I(R+r)

E = the emf of the supply in Volts.
I = the current in Amps.
R = the resistance in the external circuit.
r = the internal resistance of the supply
V = the p.d. Across the external circuit in Volts

28
Q

What is the alternative definition of emf

A

The emf of a supply is equal to the p.d. Across its terminals when it is not supplying current

29
Q

What is the potential divider equation

A

Vout = Vin x R1/R1+R2

Physics A Level (17 decks)

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