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AS Physics > Electricity > Flashcards

Electricity Flashcards

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1
Q

Conservation Of Charge

A

The law stating that charge can’t be created or destroyed, it can only be transferred and the total will always be constant

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2
Q

Coulumb

A

The unit of charge, the current that pases through a point over a given amount of time. 1 Coulumb is the equivalent of 1 amp for 1 second

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3
Q

Elementary charge

A

The charge on a single electron; -1.6 *10^-19

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4
Q

Conventional current

A

The direction of flow of current from positive to negative, opposite to the flow of electrons, original idea behind flow of charge

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5
Q

Diode

A

Allows for current only to flow in one direction

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6
Q

Forward BiasReverse Bias

A

Forward bias is when current flows in the direction allowed by a diode

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7
Q

Reverse Bias

A

Reverse bias is the flow of current against the direction of a diode

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8
Q

Internal resistance

A

The resistance within a voltage source that causes a lower voltage supply than expected when current flows

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9
Q

Drift velocity

A

The average velocity of an electron through a wire due to applying a potential difference and inducing current

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10
Q

Current

A

The rate of flow of charge, the charge flowing through a given point per second

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11
Q

Kirchhoff’s first law

A

As charge is always conserved, the sum of charges flowing into a junction must be equal to the sum of charge leaving it, the same is true for current

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12
Q

Equation for drift velocity and factors in equation?

A 
I = nAev
I = current
n = number density of charge carriers
e = charge on the particle (electron, -1.6*10^-19)
v = mean drift velocity of particle
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13
Q

Conductors

A

Large number of free charge carriers per unit volume

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14
Q

Insulators

A

Very few charge carriers per unit volume

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15
Q

Potential difference

A

The p.d. across a component describes the amount of energy per unit charge transfered to it by the charges passing through the component, measured in V

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16
Q

E.M.F

A

Electromotive force, the energy gained per unit charge by charges passing through a supply when a form of energy is transfered to electrical energy, measured in V

17
Q

Ohm’s law

A

The current through a conductor is directly proportional to the potential difference across it, provided temp is constant

18
Q

Factors that affect electrical resistance

A

Material wire is made from (more or less free electrons)
Length of the wire (longer wires, p.d is more spread amongst electrons)
Cross sectional area of wire (More electrons to flow at same drift velocity)
Temp of wire (resisting ions more energy to vibrate)

19
Q

I-V characteristics of a resistor

A

Current through a resistor is directly propotional to the pd across it

20
Q

I-V characteristic of a filament lamp

A

At low temps: like ohmic conductors

As current increases, electrons flow quicker, collisions and temp increase: resistance increases

21
Q

I-V characteristics of a diode

A

Require a threshold voltage for conduction to occur, current only in forward bias

22
Q

Resistivity

A

The measure of the resistance of a material for its cross-sectional area per unit length of the wire

23
Q

Equation for resistivity

A

RA/l
R - resistance
A - cross sectional area of wire
l - length of wire

24
Q

Equation for relationship between resistivity and temperature

A

p(t) = p(0) (1 + a (t - t(0)))
p(t) - resistivity of a material at temperature t
p(0) - resistivity at t(0) - ref temp (room temp)
a - temperature coefficient
t - temperatrue of material given
t(0) - ref temp (room temp 20*)

25
Q

Temperature coefficient

A

Value representing the relationship between the change in resistance and change in temperature of a conductor/ semi conductor

26
Q

Electrical Power

A

The rate at which energy is converted to or from electrical energy to or from another form

27
Q

Power equations

A 
Power = energy(work done) / time
Power = Current^2 * Resistance
Power = Voltage^2 / Resistance
28
Q

Kirchhoff’s second law

A

States that in any closed loop, the sum of the EMF is equal to the sum of the products of the current and resistance

29
Q

Potential divider circuit

A

A circuit that uses two resistors in series to split or divide the voltage of the supply in a chosen ratio to provide voltage to another circuit

30
Q

Terminal p.d

A

The potential difference recorded across the terminals of a cell when a current flows

31
Q

Lost volts

A

The difference between the emf of a cell and the terminal pd when a charge flows across the cell

32
Q

Internal resistance

A

The internal resistance of a source of emf is the resistance to electric current of the materials inside it, when current flows energy is transferred to these materials and the terminal pd drops

AS Physics (1 decks)

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