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A Level Physics OCR B > 3: Exam Questions > Flashcards

Flashcards in 3: Exam Questions Deck (9)
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1
Q

Why is this circuit (picture) a potential divider circuit?

A

2 Resistors connected in series

2
Q

One advantage of variable resistor potential divider circuit compared to series resistor circuit

A

1) greater range of current/pd/power control, 2) from 0

3
Q

Looking at I-V graph for an LDR: State relationship between light intensity and resistance

A

As light intensity increases the resistance decreases

4
Q

Why do you usually put a resistor in series with a LED?

A

1) the resistor limits the current in the circuit 2) otherwise it could overheat

5
Q

Explain why a variable resistor (a) circuit is better for obtaining the I-V characterisitic of the circuit than a p.divider circuit in series (b)

A

1) in (a) the voltage range is from zero to maximum possible 2) in (b) the resistance variation is small 3) in (b) voltage variation across LED is small

6
Q

In a p.divider circuit: the R of the thermistor decreases as the temp. increases. Explain why the p.d measure by the voltmerter across te fixed resistor increases as the temp. increases

A
resistance ratio R fixed / R thermistor changes
 ratio rises (so p.d. across R fixed rises)
7
Q

Here are a list of units: m⁻¹ m⁻² m⁻³ kgm⁻³ s⁻¹

Choose the correct one for charge carrier density

A

m⁻³

8
Q

Just calculated that the max. solar energy per second illuminating a photovoltaic solar panel is about 20 W.
Suggest why you might expect the actual power to be less than this [1]

A

absorbed by clouds/air/ atmospheric pollution or panel not

perpendicular to solar radiation

9
Q

A solar panel is used to recharge batteries. These batteries are used to power a lamp. Suggest and explain why the lamp is not powered directly by the solar panel [2]

A

lamp is needed in dark/er conditions/lamp needs a
constant energy source (1);
solar panel does not work in low light intensity (night)
/produces insufficient power in low light intensity/is variable
(1)