O-LevelPhysicsElectricity5054/31 · Oct/Nov 2023 · Q210 Marks
In this experiment you will investigate the resistance of a resistance wire. You are provided with: • a power source • a length of resistance wire attached to a metre rule • a resistor of resistance 10Ω • a voltmeter • connecting leads • a switch • a flying lead with a crocodile clip at the free end. The supervisor has assembled the apparatus as shown in Fig. 2.1. [Figure 2.1] The crocodile clip at the end of the flying lead may be connected at different points along the length of the resistance wire.
- (a)Close the switch. • Connect the crocodile clip attached to the flying lead to the resistance wire at the 100.0 cm mark on the metre rule. • Read the voltage V shown on the voltmeter and then remove the crocodile clip from the wire. • Record in Table 2.1 your reading of voltage V. • Repeat and record V for lengths L = 80.0cm, 60.0cm, 40.0cm and 20.0cm of the resistance wire. Remove the crocodile clip from the wire between each reading. Open the switch after you have recorded V for all lengths L. [Table 2.1: L (cm), V, I, 1/I] Calculate the current I for each length L shown in Table 2.1, using the equation I = V/10. Record your answers in Table 2.1. Calculate values of 1/I for each length L shown in Table 2.1 and record your answers in Table 2.1. Write the units in the top row of the table.[4]
- (b)(i)On the grid on page 7, plot a graph of 1/I on the y-axis against L on the x-axis. Start both axes from the origin (0,0).[2]
- (b)(ii)Draw the straight line of best fit. Extend this line to intercept the y-axis.[1]
- (b)(iii)Determine the gradient G and y-intercept c of this line. Show clearly on the graph the values you choose and show your working. gradient G = .............................................................. y-intercept c = ..............................................................[2]
- (c)Theory suggests that: R_w = 1000 G / c where R_w is the resistance of the resistance wire. Use your values in (b)(iii) to determine R_w. Show your working. R_w = .................................................... Ω[1]
This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.
Mark scheme
Marking points from the official mark scheme (Oct/Nov 2023). The mark or mark type is shown in brackets.
- [1] (a) Column headings: column headings with correct units
- [1] (a) trend of measured voltages: five voltage measurements all with V increasing as L decreases and none are zero ;
- [1] (a) calculation: values of I (V/10) and 1/I calculated correctly ;
- [1] (a) consistency: all values of I and V recorded to consistent d.p down their columns ;
- [1] (b)(i) axes: correct orientation and labelled, (1/I on y-axis, L on x-axis) plotted using suitable scale ;
- [1] (b)(i) plotting points: all points in the table plotted, to accuracy of ½ small square of grid and plot size maximum of ½ small square in diameter ;
- [1] (b)(ii) best straight line: sensible placement of a single, neat, thin, straight line even distribution of points either side of the best straight line
- [1] (b)(iii) gradient, G: Clear indication on the graph of the two sets of coordinates used to calculate G, correct substitution of two sets of (x, y) coordinates into the formula ∆y / ∆x, using two points on the BSL which are separated by at least half the length of the drawn BSL ;
- [1] (b)(iii) intercept, c: read directly from the graph to ½ small square of grid ; or use coordinates of a point on the line to substitute into y = mx + c
- [1] (c) value for Rw in range 13 ±4.0 (Ω) and working seen, correct substitution using their G and c from (b)(iii) into equation R_w = 1000 G / c ;
Write your answer and get it marked
On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.
Sign up free →