How does this potential divider circuit work?

AI Thread Summary
Changing the resistance of a variable resistor in a potential divider circuit affects the current, which subsequently alters the voltage across the other resistor. The total voltage remains constant, but the ratio of voltages across the resistors changes based on the resistance values. When the variable resistor is reduced to zero, it creates a scenario where all voltage is dropped across the other resistor. This demonstrates the principle of voltage division, confirming that option (B) is correct. Understanding these relationships is crucial for analyzing potential divider circuits.
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Homework Statement
Below is an MCQ that appeared in a GCSE exam. I am confused about the solution. Please guide.
Relevant Equations
I= V/R (Ohm's Law)
Screenshot_20240226-063918~2.png

Screenshot_20240226-063948~2.png

The correct option is supposed to be (B). Can someone please explain why changing the resistance of the variable resistor affects the voltage across the other resistor? Also explain why (B) is the correct option? Thanks
 
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changing the resistance changes the current through the circuit, which in turn changes the voltages across the resistors. The TOTAL voltage across the two can't change but the ratio clearly changes. Think in extremes. What happens if the variable resistor is taken all the way to zero?
 
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