I. Increase the melting point of the liquid.

II. Increase the boiling point of the liquid.

III. Decrease the melting point of the liquid.

IV. Decrease the boiling point of the liquid.

Which of the statement above about the effect on increase in pressure in a liquid are correct?

• A) I and II only
• B) I and III only
• C) II and III only
• D) III and IV only

A direct current cannot pass through a parallel plate capacitor because

• A. the plates are non-conducting.
• B. the dielectric between the plates is non-conducting.
• C. there is a leakage of charge from the plates.
• D. the plates have equal but opposite charges.

(a) The specific heat capacity of copper is 400 \(JKg^{-1}K^{-1}\) means that 400 J of heat energy is required to raise (or lower) the temperature of 1 kg of a piece of copper by 1 kelvin.

(b) Experiment to determine the specific heat capacity of copper using a copper ball. The piece of copper ball is suspended by a thread and placed in a beaker of boiling water. While the temperature of the copper is being raised to boiling point of water, a copper calorimeter is half filled with water. The initial temperature of the water is measured and recorded and the hot copper ball is lifted by the thread and transferred to the calorimeter when the water has reached boiling point. The calorimeter cover is put on, the mixture is well stirred and the final steady temperature read from the themometer. The copper ball is weighed either before or after the experiment. The result is tabulated as shown below.

Mass of copper ball - m (kg)

Temperature of boiling water - \(\theta\) (K)

Mass of copper calorimeter - \(m_{c}\) (kg)

Mass of calorimeter + water - \(m_{x}\) (kg)

Mass of water \((m_{x} - m_{c})\) - \(m_{w}\) (kg)

Specific heat capacity - C \((Jkg^{-1} K^{-1})\)

Initial temperature of water = \(\theta_{w}\) (K)

Final temperature of water = \(\theta_{f}\) (K)

Using Heat lost by copper ball = Heat gained by calorimeter + Heat gained by water

\(mc(\theta - \theta_{f}) = m_{c} c (\theta_{f} - \theta_{w}) + m_{w} c_{w} (\theta_{f} - \theta_{w})\)

\(c = \frac{m_{w} c_{w} (\theta_{f} - \theta_{w})}{m (\theta - \theta_{f}) - m_{c} (\theta_{f} - \theta_{w})}\)

Precautions: (i) The copper ball should be transferred quickly into the calorimeter without splashing. (ii) Just before transfer, the copper should be shaken slightly to remove adhering hot water.

(iii) Heat lost by copper ball = heat gained by copper calorimeter + Hoat gained by water.

\(m_{c} (\theta - \theta_{f}) = m c (\theta_{f} - \theta_{w}) + m_{w} c_{w} (\theta_{f} - \theta_{w})\)

\(20 \times 0.4 \times (200 - \theta_{f}) = 60 \times 0.4 \times (\theta_{f} - 30) + 50 \times 4.2 \times (\theta_{f} - 30)\)

\(8(200 - \theta_{f}) = 24(\theta_{f} - 30) + 210 (\theta_{f} - 30)\)

\(\theta_{f} = \frac{8620}{242} = 35.6K\)

In which of the following activities is an induction coil not useful?

• A. Investigation of high voltages
• B. Study of electric discharge
• C. Operation of X-ray tubes
• D. A.C. power transmission

If the frequency of the tuning fork at resonance is 256Hz, calculate the frequency of vibration of the wire when the tension in he wire is increased to 196N

• A. 130.6Hz
• B. 182.9Hz
• C. 358.4Hz
• D. 501.8Hz

When an electron jumps directly from an orbit of n = 4 to n = 2,

• A. a photon is absorbed
• B. a photon is emitted
• C. two photons are emitted.
• D. two photons are absorbed

On top of a spiral spring of the force constant 500Nm-1 is placed a mass of 5 x 10-3 kg. If the spring is compressed downwards by a length of 0.02m and then released, calculate the height to which the mass is projected

• A. 8 m
• B. 4 m
• C. 2 m
• D. 1 m

A girl whose mass is 55kg stands on a spring - weighing machine inside a lift. When the lift starts to ascend, its acceleration is 2m/s. What will be the reading on the machine? (Take g = ms^-2)

• A. 66 kg
• B. 55 kg
• C. 44 kg
• D. 22 kg

The image which cannot be formed on a screen is said to be