# Maximum voltage of battery when a diode is attached to it

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In an ideal p-n junction diode can withstand currents up to 10mA under forward bias. The diode has a potential difference of 0.5V across it which is assumed to be independent of current. What is maximum voltage of battery used to forward bias the diode when resistance of 200Ω‎ is connected in series with it.

I understand that I should apply $V = IR$ to this scenario but I'm not sure how to apply this with the diode?

asked Nov 4, 2016
edited Nov 4, 2016
Please show your thoughts on this question and then we will help you out. At least write out the relevant equations along with stating exactly where you are getting stuck. See the meta post : http://physicsproblems.nfshost.com//?qa=116/scope-%26-guidelines
Thanks for your question Junaid and welcome to the site :-)

## 1 Answer

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Best answer

Let $V$ be the voltage of the battery.

The voltage over the diode is given to be $0.5$ and therefore the voltage over the resistor is given by $V - 0.5$.

Using $V = IR$ we can compute the current over the resistor,

$I = \frac{V}{R} = \frac{V-0.5}{200}$

Since the maximum current in the circuit is $0.01A$, we can find the maximum voltage of the battery by solving the equation,

$0.01 = \frac{V-0.5}{200}$

Therefore,

$V = 2.5$ Volts

answered Nov 4, 2016 by (1,486 points)
selected Nov 4, 2016