Numeracy Higher June 2019 Unit 1 Q9
9. The voltage, \(V\) volts, of an electric circuit is given by the formula
\[V = IR,\]where \(I\) is the current measured in amps, and \(R\) is the resistance measured in ohms.
During an experiment,
- \(V\) was measured at 280 volts, correct to the nearest 10 volts,
- \(I\) was measured at 0·2 amps, correct to the nearest 0·1 amps.
Calculate the least possible value and greatest possible value of the resistance \(R\). [6]
Least possible value of \(R\) = …………………… ohms
Greatest possible value of \(R\) = …………………… ohms
| Scheme | Marks | Comments |
|---|---|---|
| Use of 275 (volts) AND 285 (volts) OR Use of 0.15 (amps) AND 0.25 (amps) | B1 | Accept use of \(0.24\dot{9}\) and \(284.\dot{9}\) throughout, but do not accept use of 0.249 and 284.9 |
| \(\dfrac{V}{I} = R\) | B1 | May be implied in further working |
| (Least possible value of R =) \(\dfrac{275}{0.25}\) | M1 | FT 'their 275' provided 270 < V < 280 AND 'their 0.25' provided 0.2 < I < 0.3 |
| = 1100 (ohms) | A1 | CAO |
| (Greatest possible value of R =) \(\dfrac{285}{0.15}\) | M1 | FT 'their 285' provided 280 < V < 290 AND 'their 0.15' provided 0.1 < I < 0.2 |
| = 1900 (ohms) | A1 | CAO |