# $V$-$I$ characteristics and circuits [closed]

The only solution stuck in my head goes through finding the resistance from the slope of the curves and using it somehow in the solution, however, I can't figure out what voltage do I use for X and Y? (The current will obviously be the same for both.)

How does one approach exercises of this type?

Two resistors, X and Y, have I–V characteristics given by the graph. The resistors X and Y are connected in series to the same cell. Estimate the total current leaving the cell in this circuit.

P. S. The resistors X and Y connected to a cell of emf 1.5 V • What is the voltage of the cell? Apr 28 at 19:01
• I've included it. Apr 28 at 19:03
• OK. Now, the current is the same through each resistor since they are in series. So, how can you figure out the current? Apr 28 at 19:06
• Forget equations - solve it using the graph. Apr 28 at 19:25
• should the current be such that the voltage adds up to 1.5V or something like that? Apr 28 at 19:31

The slope of the $$I\ \text{against}\ V$$ curve gives the reciprocal of the so-called 'slope resistance', $$\frac{dV}{dI}$$. This can be a useful concept, but it's not relevant here.

Here are some hints as to how to proceed...

• What quantity is the same for both resistors?

• A family of straight lines can be imagined to be drawn on the graph grid. Each straight line represents a particular value of this quantity.

• What is the relationship between the voltages across X and Y and the voltage provided by the cell?

• If you knew the cell voltage you'd be able to select which of the lines that you imagined is the right one!

The current is the same thorough both resistors; the total voltage drop across both resistors is 1.5 V (neglecting resistive losses in the battery). With these constraints, using the graphs, you can calculate the current. What do you calculate for the current?