| Date | November 2017 | Marks available | 1 | Reference code | 17N.3.SL.TZ0.2 |
| Level | Standard level | Paper | Paper 3 | Time zone | Time zone 0 |
| Command term | State | Question number | 2 | Adapted from | N/A |
Question
An electrical circuit is used during an experiment to measure the current I in a variable resistor of resistance R. The emf of the cell is e and the cell has an internal resistance r.
A graph shows the variation of \(\frac{1}{I}\) with R.
Show that the gradient of the graph is equal to \(\frac{1}{e}\).
[2]
a.
State the value of the intercept on the R axis.
[1]
b.
Markscheme
«ε = IR + Ir»
\(\frac{1}{I} = \frac{R}{\varepsilon } + \frac{r}{\varepsilon }\)
identifies equation with y = mx + c
«hence m = \(\frac{1}{\varepsilon }\)»
No mark for stating data booklet equation
Do not accept working where r is ignored or ε = IR is used
OWTTE
a.
«–» r
Allow answer in words
b.
Examiners report
[N/A]
a.
[N/A]
b.
