current, potential difference, power and resistance Flashcards

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1
Q

what are voltage dividers used for?

A

to set an input voltage to a control circuit

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2
Q

what are potential dividers?

A

simple series circuits with two or more resistors. the bigger resistor will have a bugger potential difference across it.

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3
Q

how to work out potential difference across resistor

A

could calculate current flowing in circuit (Vs/RT) then voltage across resistor V=IR2

easier to use equation V1=(R1/R1+R2) Vs

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4
Q

ratio of resistance R1:R2, voltage…

A

splits in same ratio

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5
Q

rule for current in series

A

same at all points

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6
Q

rule for current in parallel

A

sum to supply current

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7
Q

rule for voltage in series

A

sum to supply voltage

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8
Q

rule for voltage in parallel

A

same at all points

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9
Q

power definition

A

the energy transferred every second

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10
Q

power equations

A

P=IV
P=I squared R
P= V squared / R

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11
Q

measuring resistance using ammeter/voltmeter involves some error unless…

A

resistance of meters is taken into account

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12
Q

only situation where errors with using ammeter/voltmeter don’t matter is…

A

if the reading on the meter is zero

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13
Q

Wheatstone Bridge Circuit

A

-the voltmeter forms a ‘bridge’ between the two voltage dividers to make up a bridge circuit

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14
Q

no potential difference will exist across AB when…

A

R1/R2 = R3/R4

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15
Q

if Voa=Vob…

A

there is no potential difference between A and B so no current flows

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16
Q

the potentials at A and B depend on…

A

the ratio of the resistors that make up each of the two voltage dividers

17
Q

If bridge is balanced then resistor is altered by a small amount then…

A

out of balance potential difference is directly proportional to change in resistance

V1/V2 = R1/R2