10.3 AS Level

Potential dividers

7 flashcards to master this topic

Definition Flip

State the principle of a potential divider circuit.

Answer Flip

A potential divider circuit divides a voltage source into smaller output voltages. The output voltage across a resistor in the series is proportional to its resistance relative to the total resistance in the circuit. V_out = V_in * (R_out / R_total)

Key Concept Flip

Explain how a potentiometer can be used to compare potential differences.

Answer Flip

A potentiometer balances an unknown potential difference against a known variable potential difference. When the galvanometer shows zero current (null method), the unknown potential difference is equal to the known potential difference at that position on the potentiometer.

Definition Flip

What is the purpose of a galvanometer in null methods?

Answer Flip

A galvanometer in a null method acts as a sensitive current detector. It indicates when the potential difference across two points is zero, allowing for precise measurements.

Key Concept Flip

How does a thermistor affect the output voltage of a potential divider as temperature increases?

Answer Flip

Typically, thermistors have a negative temperature coefficient (NTC). As temperature increases, the resistance of the thermistor decreases. This changes the voltage division, typically causing the output voltage across the thermistor to decrease (if the thermistor is in the bottom half of the divider).

Key Concept Flip

How does a light-dependent resistor (LDR) affect the output voltage of a potential divider as light intensity increases?

Answer Flip

As light intensity increases, the resistance of an LDR decreases. This changes the voltage division, typically causing the output voltage across the LDR to decrease (if the LDR is in the bottom half of the divider).

Calculation Flip

In a potential divider with two resistors R1 and R2 in series with a voltage source V, what is the formula for the voltage across R2 (V_R2)?

Answer Flip

V_R2 = V * (R2 / (R1 + R2)), where V is the total voltage, R1 and R2 are the resistances of the resistors.

Calculation Flip

A potential divider consists of a 1000Ω resistor and a thermistor in series with a 5V supply. At 25°C, the thermistor's resistance is 500Ω. Calculate the voltage across the thermistor.

Answer Flip

V_thermistor = 5V * (500Ω / (1000Ω + 500Ω)) = 5V * (500/1500) = 1.67V

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