An IGCSE physics class is investigating the resistance of a constantan wire of different lengths. A student measures the current III in the circuit and the potential difference VVV across various lengths lll of the wire.
The readings are shown in the table below:
| l/l/l/ | V/V/V/ | I/I/I/ | R/R/R/ |
|---|---|---|---|
| 0.2000.2000.200 | 0.480.480.48 | 0.400.400.40 | |
| 0.4000.4000.400 | 0.940.940.94 | 0.390.390.39 | |
| 0.6000.6000.600 | 1.481.481.48 | 0.410.410.41 | |
| 0.8000.8000.800 | 1.881.881.88 | 0.390.390.39 | |
| 1.0001.0001.000 | 2.422.422.42 | 0.400.400.40 |
Calculate the resistance RRR of each length lll of wire using the equation R=VIR = \frac{V}{I}R=IV. Record the values of RRR to two decimal places.
Complete the heading for each column of the table by identifying the correct standard unit for each quantity.
Calculate the gradient GGG of the relationship between resistance and length using the values for l=0.200 ml = 0.200\text{ m}l=0.200 m and l=1.000 ml = 1.000\text{ m}l=1.000 m:
G=Rat 1.000 m−Rat 0.200 m1.000 m−0.200 m G = \frac{R_{\text{at } 1.000\text{ m}} - R_{\text{at } 0.200\text{ m}}}{1.000\text{ m} - 0.200\text{ m}} G=1.000 m−0.200 mRat 1.000 m−Rat 0.200 mState the unit of GGG.
Predict the resistance RxR_xRx of a 1.50 m1.50\text{ m}1.50 m length of this wire. State your answer to 2 or 3 significant figures.
452 exam-style questions on CIE IGCSE Physics 4.2 Electrical quantities, covering 4.2.1a Positive and negative charge, 4.2.1b Charging by friction and detecting charge, 4.2.1c Electrical conductors and insulators, 4.2.1d Electric fields and electric field patterns, 4.2.2a Electric current, charge and measuring current, 4.2.2b Conduction in metals and the direction of current, 4.2.2c Direct current and alternating current, 4.2.3a Electromotive force, 4.2.3b Potential difference and voltmeters, 4.2.4a Resistance, 4.2.4b Resistance of a metallic wire, 4.2.4c Current–voltage graphs, and 4.2.5 Electrical energy and electrical power. Each one has a worked solution and a mark scheme showing where the marks go.