During a stage rehearsal, a technician tests a small filament lamp used as a warning light in a control box. The technician increases the voltage in the cir...
Question 1 Report
During a stage rehearsal, a technician tests a small filament lamp used as a warning light in a control box. The technician increases the voltage in the circuit and measures the current. Table 1 gives the readings. Some electrical energy transferred to the lamp becomes light and some heats the filament.
Table 1
| voltage / V | current / A |
|---|---|
| 0.0 | 0.00 |
| 1.0 | 0.18 |
| 2.0 | 0.31 |
| 3.0 | 0.40 |
| 4.0 | 0.46 |
(a) State the quantity that should be plotted on the horizontal axis of a graph of these results. [1]
(b) Plot the results on the grid provided and draw a smooth line of best fit. [3]
(c) Calculate the resistance of the filament when the voltage is 3.0 V. [2]
(d) Explain why the graph is not a straight line as the voltage is increased. [3]
Answer Details
(a) Plot voltage, or potential difference, in V on the horizontal axis because it is the quantity deliberately changed. [1]
(b) The graph uses voltage on the horizontal axis and current on the vertical axis. All measured points are plotted, with a smooth curve of best fit.
[3]
(c)
\[R=\frac{V}{I}=\frac{3.0}{0.40}=7.5\ \Omega\]
Resistance = \(7.5\ \Omega\). [2]
(d) Increasing current heats the filament. Its temperature rises, increasing its resistance. Therefore each further increase in voltage gives a smaller increase in current, producing a curve rather than a straight line. [3]
Download The App On Google Playstore
Everything you need to excel in your exams
