WAEC Physics 2020 Objective — Question 18
Question 18 of 50 from the West African Examinations Council (WAEC) Physics 2020 Objective paper, with the correct answer and a full explanation.
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The length of an iron bar is 100 cm at 20C. At what temperature will its length increase by 0.01%? [Linear expansivity of iron=1.2x10^-5 C^-1]
- A. 48.0 C
- B. 38.0 C
- C. 28.3 CCorrect
- D. 23.0 C
Explanation
Given original length l0=100cm, theta1=20C. Since length increases by 0.01%, delta_l=0.01cm. alpha=delta_l/(l0 x delta_theta), so delta_theta=delta_l/(l0 x alpha)=0.01/(100x1.2x10^-5)=8.3. theta2=theta1+delta_theta=20+8.3=28.3C.
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