A steel ruler A, a steel ruler B and a rod of steel are made of the same material. The steel ruler A is accurate at +20 °C. The steel ruler B is accurate when used at − 3 0 ∘ C . Use these two rulers

Question

A steel ruler A, a steel ruler B and a rod of steel are made of the same material. The steel ruler A is accurate at +20 °C. The steel ruler B is accurate when used at − 3 0 ∘ C . Use these two rulers at − 30 ∘ C to measure the length of the above-mentioned rod of steel. The readings are ℓ A ​ and ℓ B ​ respectively, and at +20 °C temperature, use these two rulers to measure the length of the rod. The readings are ℓ ′ A ​ and ℓ ′ B ​ respectively, then :-

TestHub · Accepted Answer

At − 3 0 ∘ C : ruler B reads true; ruler A's divisions have contracted, so A reads high: ℓ A ​ > ℓ B ​ At + 2 0 ∘ C : ruler A reads true; ruler B's divisions have expanded, so B reads low: ℓ A ′ ​ > ℓ B ′ ​ Answer (A, C)

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