3: Exam Questions Flashcards
Why is this circuit (picture) a potential divider circuit?
2 Resistors connected in series
One advantage of variable resistor potential divider circuit compared to series resistor circuit
1) greater range of current/pd/power control, 2) from 0
Looking at I-V graph for an LDR: State relationship between light intensity and resistance
As light intensity increases the resistance decreases
Why do you usually put a resistor in series with a LED?
1) the resistor limits the current in the circuit 2) otherwise it could overheat
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)
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
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
resistance ratio R fixed / R thermistor changes ratio rises (so p.d. across R fixed rises)
Here are a list of units: m⁻¹ m⁻² m⁻³ kgm⁻³ s⁻¹
Choose the correct one for charge carrier density
m⁻³
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]
absorbed by clouds/air/ atmospheric pollution or panel not
perpendicular to solar radiation
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]
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)
