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physics > P2 > Flashcards

P2 Flashcards

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1
Q

What is a series circuit?

A

Series circuit has no branches and the current can only flow in one path

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2
Q

What is current?

A

An electric current is a flow of electric charge around a circuit
Unit amp(a)

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3
Q

How do you measure Current?

A

You can measure current in a circuit by using an ammeter

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4
Q

What is a parallel circuit?

A

A parallel circuit contains branches and splits currents between branches

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5
Q

What is the current like in the parallel circuits?

A

The current in the branches adds up to the total current leaving the cell

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6
Q

What is potential difference?

A

measure of energy, per unit of charge, transferred between two points in a circuit

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7
Q

What we used to measure potential difference

A

Volt meter

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8
Q

What is the potential difference in parallel circuits like?

A

For components connected in parallel the potential difference across each component is the same

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9
Q

what is electrical charge

A

Electric charge is an amount of electricity that is held in or carried by something.
a current of one amp = 1 coulomb of charge flowing per second

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10
Q

what is the equation for charge flow

A

q=lxt
charge flow =currentxtime

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11
Q

What is resistance ?

A

Resistance tells us the potential difference required to drive a current through a component

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12
Q

What is the equation for energy transferred?

A

E=QxV
Energy transferred (G) = charge flow (C) x potential difference (V)

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13
Q

What is the equation for resistance?

A

R=V/I
Resistance=pd/current

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14
Q

what is DC?

A

direct current produced from a cell

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15
Q

what is an AC?

A
  • Alternating current and an example is uk mains
  • in uk AC frequency is 50Hz
    -PD is 230 volts
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16
Q

what are benifits of AC?

A
  • very easy to use a transformer to increase or decrease the pd
17
Q

what is the brown live wire used for?

A

-carries the alternating potential difference from the supply(230v)
-connected to the fuse in the plug

18
Q

what is the blue neutral wire used for?

A

completes the circuit and has a pd of 0 compared to the live wire

19
Q

what is the green and yellow safety wire used for?

A

-stops the appliances from becoming live

20
Q

what is the national grid?

A

the national grid consists of a system of transformers and high voltage cables

21
Q

what does a step up transformer do?

A

increase potential difference to several hundred thousand volts so less energy is lost within the power cables

22
Q

what is uncertainty

A

due to random error scientists cannot be certain of the accurate or true value of measurement

23
Q

how do we calculate uncertainty

A

range of values/2

24
Q

what is the equation that links power current and resistance

A

power=current^2 x resistance

25
Q

what is the resistance of an LDR like

A

-Resistance of an LDR is low in the light
-Resistance changes depending on light intensity

26
Q

what happens to the ammeter in a circuit if resistance of the circuit decreases

A

-more current is allowed to flow through the circuit

27
Q

what happens to the voltmeter if the resistance of the component its reading decreases

A

-the voltmeter would get less share of PD
-the reading of the voltmeter will decrease

28
Q

how should we change the circuit to give negative values for current and PD

A

reverse connections to the cell

29
Q

relationship between current and pd for a resistor at constant temp

A

directly proportional

30
Q

differences between AC and DC

A

-direct current is always in the same direction
-alternating current changes direction

31
Q

when connecting to the uk mains why is it beneficial to use a low resistance cable

A

-lower potential difference across
the cable
-it is more efficient

32
Q

calculation for resistance

A

PD/current

33
Q

what is the resistance of resistors connected in parallel

A

the total resistance of two resistors in parallel is less than the resistance of the smallest individual resistor

34
Q

student increased the temperature of the thermistor.
Explain how the current in the thermistor changed.

A

-the current increased
-(because) the resistance (of the
thermistor) decreased

35
Q

The heating element of the kettle was connected to the mains supply.
Explain why the temperature of the heating element increased.

A

-electrons collide with particles in
the heating element
-which increases the (kinetic)
energy of the particles

36
Q

measuring using a geiger muller tube
explain why count rate of a radioactive sample is less then activity

A

-the source spreads radiation in every direction
-the geiger muller tube only measures the radiation that passes through

physics (9 decks)

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