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GCSE Physics LTS > Circuit investigations > Flashcards

Circuit investigations Flashcards

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1
Q

Why do we repeat readings

A

We repeat readings to find any anomalous results

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2
Q

Why do we calculate an average

A

We calculate an average from our repeated readings to eliminate the effect of random errors

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3
Q

Draw the circuit diagram for investigating current and voltage for a resistor

A

Include
Variable Power supply
Ammeter
Resistor
Voltmeter connected to the resistor in parallel
Switch

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4
Q

State the method for investigating current and voltage for a resistor

A

With the power supply off, set up the circuit
Increase the voltage, close the switch and record readings from the ammeter and voltmeter
Repeat this method, for higher voltages
Swap the connections of the power supply and repeat the whole experiment for negative values of current and voltage

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5
Q

Draw the graph for investigating current and voltage for a resistor

A

Straight line passing through the 1st quadrant and the 3rd quadrant
Voltage - on x-axis
Current - on y-axis

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6
Q

Using the graph, a conclusion for investigating current and voltage for a resistor

A

The graph is a straight line through the origin, therefore the current is directly proportional to the voltage (Current ∝ Voltage) - (as voltage doubles, current doubles)

This applies to both positive and negative values of voltage and current

This is true if resistance is constant
This is true for a resistor (and any conductor if its temperature is constant

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7
Q

Use the graph for investigating current and voltage for a resistor, to calculate resistance

Voltage = 10V
Current = 2.3A

A

E.g.
Go up from 10V until you hit the line - 2.3A
Voltage = 10V
Current = 2.3A
When voltage is 10, current is 2.3

Gradient = ∆y/∆x = 2.3/10 = 0.23 = I/V
Resistance = V/I = 1/gradient = 1/0.23 = 4.3Ω (to 1 d.p.)

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8
Q

Draw the circuit diagram for investigating the current and voltage for a diode

A

See book

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9
Q

Using a diode, how do you know which direction in which the current flows

A

The direction of the arrow of a diode represents the direction in which the current moves

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10
Q

State the method for investigating the current and voltage for a diode

A

Using the Potential divider, vary the voltage that the diode recieves

As the voltage is increased, record readings from the ammeter and voltmeter
To obtain negative values of current and voltage, swap the connections of the power supply

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11
Q

Draw the graph for investigating the current and voltage for a diode

A

Graph showing 1st and 2nd quadrants
https://bam.files.bbci.co.uk/bam/live/content/zwmb7p3/large

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12
Q

Using the graph write a conclusion for investigating the current and voltage for a diode

A

A diode only allows current to flow in one direction.
If the potential difference is arranged to try and push the current the wrong way (also called reverse-bias) no current will flow as the diode’s resistance remains very large.
Current will only flow if the diode is forward-biased.
When forward-biased, the diode’s resistance is very large at low potential differences but at higher potential differences, the resistance quickly drops and current begins to flow.

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13
Q

What is the threshold voltage - in terms of for investigating the current and voltage for a diode

A

The threshold voltage is the voltage when the current starts to flow

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14
Q

Name the graph with a straight line through the origin

A

The current-potential difference graphs for a resistor at constant temperature

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15
Q

Name the graph that curves - identify the component this relates with

A

Filament lamp

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16
Q

Name the graph where current is 0, then increases rapidly - identify the component this relates with

A

Diode

17
Q

Describe the resistance of an LDR in the dark

A

In the dark, a LDR has a very high resistance

18
Q

Describe the resistance of an LDR in light

A

In light, the LDR has a very low resistance

19
Q

What is the LDR used for

A

The LDR is used as a light sensor

20
Q

Describe the resistance of a thermistor when it is cold

A

When it is cold, the thermistor has a very high resistance

21
Q

Describe the resistance of a thermistor when it is hot

A

When a thermistor is hot, it has a very low resistance

22
Q

What are thermistors used for

A

Thermistors are used as a temperature sensor

23
Q

Draw the symbols for:
switch (open)
switch(closed)
cell
battery
Diode
Resistor
Variable resistor
Lamp
Fuse
Voltmeter
Ammeter
Thermistor
LDR
LED

A

https://bam.files.bbci.co.uk/bam/live/content/z3cxgdm/large

24
Q

Draw the circuit diagram for an automatic lighting circuit/system

A

Includes
Battery, LDR, Variable resistor, A bulb connected in parallel to the LDR

25
Q

Explain how the automatic lighting circuit/system works

A

When it is light, the resistance of the light dependent resistor is low, therefore the voltage across it is also low

The bulb in parallel, with the light dependent resistor, receives the same voltage, and is therefore off.

When it is dark, the resistance of the LDR is very high, it therefore receives a much higher voltage, the bulb receives the same voltage and switches on

The variable resistor controls the sensitivity of the circuit, if it’s resistance is high, then it must be much darker for the light to switch on

26
Q

Draw the graph for investigating the current and voltage for a diode

A

Graph showing 1st and 2nd quadrants
https://bam.files.bbci.co.uk/bam/live/content/zwmb7p3/large

GCSE Physics LTS (30 decks)

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