Question

in determining the depth of an ocean an echo sounder produces ultrasonic sound. give reasons why ultra sound is preferred for this purpose. (2 marks)

1. sketch a magnetic field pattern around two conductors as shown below. (2 marks)

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1. (a) give a reason why a clinical thermometer should never be sterilized using boiling water. (1 mk)

(b) what do you understand by anomalous expansion of water? (1 mark)

1. two flasks a and b were placed on a horizontal surface as shown in figure 2

a (empty flask) b (partly filled with water)
state and explain which flask is more stable. (2 marks)

1. the weight of a solid in air is 5.0n. when it is fully immersed in a liquid of density 800kgm-3 its weight is 4.04n. determine the upthrust in the liquid. (2 marks)

Explanation:

• Ultrasound preference: High frequency reduces energy loss, enabling clear echo detection for accurate depth measurement.
• Magnetic field sketch: Requires right-hand grip rule (not visualizable here; fields around parallel conductors with inward current form concentric circles, repelling between conductors).
• 11(a): Clinical thermometers have a max temp ~42°C; boiling water (100°C) would break the glass or damage the device.
• 11(b): Water expands when cooled from 4°C to 0°C (opposite to normal thermal contraction).
• 12: Flask B is more stable—water lowers its center of gravity, increasing stability.
• 13: Upthrust = weight in air - apparent weight in liquid.

Answer:

• Ultrasound is preferred because it has high frequency, minimizing energy loss and producing distinct echoes for precise depth calculation.
• (Sketch: Concentric circles around each conductor, with repulsion between them.)
• 11(a): Boiling water temperature (100°C) exceeds the clinical thermometer's maximum range (~42°C), causing damage.
• 11(b): Water expands as it cools from 4°C to 0°C instead of contracting.
• 12: Flask B is more stable; the water lowers its center of gravity.
• 13: 0.96N