Question

What resistance should a resistor be to be used as a part of a voltage divider along a 1.2 kΩ resistor? The potential difference across the 1.2 kΩ resistor is to be 2.2 V when the supply is 12 V. 1.2 kΩ

Answer 1

Given:

Potential difference supplied is 12 V

Resistor is 1200 ohm

Max potential difference across that resistance is 2.2 V

To find:

Additional resistance used as voltage divider ?

Concept:

If an additional resistance is used in series with 1200 ohm resistor in series combination , the potential difference from the supply gets divided but current remains constant.

Calculation:

Let additional resistance be x .

Equivalent resistance of Circuit will be :

$\therefore \: R \:eq. = x + 1200$

Current in the circuit will be :

$\therefore \:I = \dfrac{V}{R \:eq.}$

$=>I = \dfrac{12}{x + 1200}$

Now potential difference across the 1200 ohm will be 2.2 V as per the question :

$\therefore\: 2.2 = \dfrac{12}{x + 1200}\times 1200$

$= > 1200 + x = \dfrac{12 \times 1200}{2.2}$

$= > 1200 + x = 6545.45$

$= > x = 5345.45 \: ohm$

So the additional resistance will be 5345.45 ohm.