# AS Coursework

i am currently doin my as level coursework and for part of it i need to work out what size resistor to use in a potential divider but i have no idea how anyone that could help i would be really grateful,,

thanx
steph xx

## Answers and Replies

Kurdt
Staff Emeritus
Gold Member
It depends what one wants to do with the potential divider. That is, what is the input voltage and the output voltage that you want?

umm.. well we have to put 9 volts in but im not sure what voltage out,, we are making a sensor,, we are designing the ciruit so when the light level fall too low a bulb will switch on

Kurdt
Staff Emeritus
$$V_{out} =\frac{R_2}{R_1+R_2} V_{in}$$