Photo AI
This question is about a resistance wire made of nichrome - OCR - A-Level Physics A - Question 1 - 2018 - Paper 1
Question 1
This question is about a resistance wire made of nichrome. (a)* It is suggested that the resistance R of a length of nichrome wire varies with temperature θ in °C a... show full transcript
Worked Solution & Example Answer:This question is about a resistance wire made of nichrome - OCR - A-Level Physics A - Question 1 - 2018 - Paper 1
Step 1
Describe how you would carry out the experiment, abuse the data to verify the relationship between R and θ and determine a value for k.
Answer
To carry out the experiment, follow these steps:
- Setup the Apparatus: Assemble the apparatus as shown in Fig. 1.1 with the nichrome wire submerged in a water bath. Ensure all connections are secure and that the thermometer is positioned correctly to measure the water temperature.
- Heating the Wire: Gradually heat the water using a d.c. supply, and allow sufficient time for the temperature to stabilize before taking measurements.
- Record Measurements: For various temperatures (record using the thermometer), measure and record the resistance of the nichrome wire using a voltmeter and ammeter to calculate R = V/I.
- Plotting the Data: Create a graph of R against θ using the data collected. The slope of the line will help establish the value of k by using the relationship derived from the equation of a straight line.
- Improving Accuracy: To improve accuracy, ensure the wire does not touch the beaker's sides and that there’s even heat distribution. Perform repeat measurements and consider using more precise measuring equipment.
Step 2
Show that the length of wire wound on the heating element is 3.5 m.
Answer
To show that the length of the wire is 3.5 m, use the following steps:
-
Convert Power to Resistance: The power (P) of the heating element is 1.0 kW, and voltage (V) is 230 V. Using the formula:
P = rac{V^2}{R}
Rearranging gives us:
R = rac{V^2}{P} = rac{230^2}{1000} = 52.3 Ω -
Calculate the Length:
The resistance of nichrome is given by:
ho rac{L}{A} $$
Using the cross-sectional area from the data for swg and substituting values, solve for length (L).
Step 3
Use the information given in (i) and (ii) to determine the swg number of the wire used as the heating element.
Answer
To determine the swg number, follow these steps:
- Apply Resistivity Data:
Use the data for resistivity and previously calculated length and area:
ho rac{L}{A} $$
Solving for A will lead to the identification of the corresponding swg number.
2. Reference the Table:
Compare calculated diameter with the standard table of swg values.
3. Conclusion:
From the calculations, conclude that for our parameters, the swg number is found to match with appropriate cross-sectional area data.