Define potential divider .

A potential divider is a circuit that produces an output voltage as a fraction of the input voltage , using two resistors in series to divide the supply voltage in a chosen ratio.

Define potentiometer .

A potentiometer is a variable resistor connected as a potential divider that gives a continuously variable output voltage, using a sliding contact along a resistance coil.

In a potential divider, the resistor with the largest resistance has the .......... potential difference.

In a potential divider, the resistor with the largest resistance has the greatest potential difference.

State two purposes of a potential divider circuit.

To provide a variable potential difference, and to enable a specific potential difference to be chosen from a supply.

Define light-dependent resistor (LDR) .

A light-dependent resistor (LDR) is a resistor whose resistance decreases as light intensity increases .

A thermistor is a resistor whose resistance decreases as temperature increases .

Give two devices that use an LDR in a potential divider circuit.

Street lights and security lights (also used in light meters).

Give two devices that use a thermistor in a potential divider circuit.

Fire alarms , ovens and digital thermometers .

If the resistance of an LDR or thermistor .......... , the potential difference across it also decreases.

If the resistance of an LDR or thermistor decreases , the potential difference across it also decreases.

True or False? The resistance of a thermistor increases as temperature increases.

False. The resistance of a thermistor decreases as temperature increases .

In a potential divider with a fixed resistor and a thermistor, what happens to the potential difference across the fixed resistor when the potential difference across the thermistor increases?

It decreases , since the potential differences across both components must sum to the constant e.m.f. of the supply.

What are the independent and dependent variables in the LDR calibration experiment?

Independent variable: light intensity (lux). Dependent variable: potential difference across the resistor (V).

What are the independent and dependent variables in the thermistor calibration experiment?

Independent variable: temperature (°C). Dependent variable: potential difference across the resistor (V).

What is the control variable in the LDR and thermistor calibration experiments?

The e.m.f. of the power supply .

Define calibration curve (for these investigations).

A calibration curve is a graph of potential difference against light intensity (or temperature), used to find an unknown light intensity (or temperature) from a measured potential difference.

How can random errors be reduced in these calibration curve experiments?

Repeat the potential difference measurements, and take readings over as wide a range as possible to obtain many data points.

To avoid a systematic (zero) error, make sure the voltmeter and digital light sensor .......... before taking readings.

To avoid a systematic (zero) error, make sure the voltmeter and digital light sensor read zero before taking readings.

True or False? The temperature of the thermistor is measured directly, so no assumption is needed about the water's temperature.

False. The thermistor's temperature is assumed to equal the water's temperature, so the water must be stirred thoroughly to keep it even.

A LevelPhysicsOCRFlashcards4. Electrons, Waves & PhotonsPotential Dividers

Potential Dividers (OCR A Level Physics): Flashcards

Exam code: H556

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FrontPotential Divider Circuits
Define potential divider.

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Cards in this collection (21)

Define potential divider.
A potential divider is a circuit that produces an output voltage as a fraction of the input voltage, using two resistors in series to divide the supply voltage in a chosen ratio.
Define potentiometer.
A potentiometer is a variable resistor connected as a potential divider that gives a continuously variable output voltage, using a sliding contact along a resistance coil.
What is the potential divider equation for $V_{o u t}$ in terms of $R_{2}$ ?
$V_{o u t} = \frac{R_{2}}{R_{1} + R_{2}} V_{i n}$
Which resistance must go in the numerator of the potential divider equation?
The resistance of the resistor across which $V_{o u t}$ is measured.
In a potential divider, the resistor with the largest resistance has the .......... potential difference.
In a potential divider, the resistor with the largest resistance has the greatest potential difference.
True or False?
The potential difference across a resistor is inversely proportional to its resistance, from $V = I R$ .
False.
From $V = I R$ , the potential difference across a resistor is directly proportional to its resistance (for a constant current).
State two purposes of a potential divider circuit.
To provide a variable potential difference, and to enable a specific potential difference to be chosen from a supply.
Define light-dependent resistor (LDR).
A light-dependent resistor (LDR) is a resistor whose resistance decreases as light intensity increases.
Define thermistor.
A thermistor is a resistor whose resistance decreases as temperature increases.
Give two devices that use an LDR in a potential divider circuit.
Street lights and security lights (also used in light meters).
Give two devices that use a thermistor in a potential divider circuit.
Fire alarms, ovens and digital thermometers.
If the resistance of an LDR or thermistor .........., the potential difference across it also decreases.
If the resistance of an LDR or thermistor decreases, the potential difference across it also decreases.
True or False?
The resistance of a thermistor increases as temperature increases.
False.
The resistance of a thermistor decreases as temperature increases.
In a potential divider with a fixed resistor and a thermistor, what happens to the potential difference across the fixed resistor when the potential difference across the thermistor increases?
It decreases, since the potential differences across both components must sum to the constant e.m.f. of the supply.
What are the independent and dependent variables in the LDR calibration experiment?
Independent variable: light intensity (lux). Dependent variable: potential difference across the resistor (V).
What are the independent and dependent variables in the thermistor calibration experiment?
Independent variable: temperature (°C). Dependent variable: potential difference across the resistor (V).
What is the control variable in the LDR and thermistor calibration experiments?
The e.m.f. of the power supply.
Define calibration curve (for these investigations).
A calibration curve is a graph of potential difference against light intensity (or temperature), used to find an unknown light intensity (or temperature) from a measured potential difference.
How can random errors be reduced in these calibration curve experiments?
Repeat the potential difference measurements, and take readings over as wide a range as possible to obtain many data points.
To avoid a systematic (zero) error, make sure the voltmeter and digital light sensor .......... before taking readings.
To avoid a systematic (zero) error, make sure the voltmeter and digital light sensor read zero before taking readings.
True or False?
The temperature of the thermistor is measured directly, so no assumption is needed about the water's temperature.
False.
The thermistor's temperature is assumed to equal the water's temperature, so the water must be stirred thoroughly to keep it even.

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