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Model Sample Paper - 7

Q.1. It is easier to start a car on a warm day than on a chilly day, why?

Q.2. Does negative magnitude of star mean more brightness or less brightness.

Q.3. When the motor of an electric refrigerator starts, lights in the house become dim momentarily, Why ?

Q.4. How focal length of a lens changes when it is immersed in water? What happens to the focal length of a mirror immersed completely in water ?

Q.5. What is the role of soft iron core in a moving coil galvanometer?

Q.6. Why is zinc rod not allowed to remain in the acid when the Daniel cell is not in use?

Q.7. What happens to magnifying power of a microscope, when length of its tube is increased?

Q.8. A concave mirror and a convex lens are held in water. What change if any, d, you expect to find in focal length of either?

Q.9. State and explain low of Malus.

Q.10. Describe the path of a charged particle moving in a uniform magnetic field wit initial velocity (i) perpendicular 'to the field (ii) at an arbitrary angle with the, field direction.

Q.11. How will you estimate surface temperature of a planet? Explain.

Q.12. A tank is filled with water to a height of 12.5 em. The apparent 'depth o a needle lying at the bottom of the tank is measured by a microscope to be 9.4 cm. What is the refractive index of water? If water is replaced by a liquid of refractive index 1.63 upto the same length by what distance would the microscope have to be moved to focus on the, needle again.

Q.13. What happens if a bar magnet is cut into two piece (i) transverse to its length (ii) along its length? What is magnetic moment of the pieces obtained in each case?

Q.14. An ordinary moving coil ammeter used for D.C. cannot be used to measure alternating current even if its frequency is low. Explain, why?

Q.15. What is the role of space wave propagation in transmission of high frequency signals?

16. Prove that m = (1/sinC), where C is the critical angle.

Q.17. Half-life of a sample is 20 minutes. In how much time will the activity of sample, drop to 1/16 of its initial value?

Q.18. How can an OR gate be realized from the NAND gate?

Q.19. Explain the action of p-n-p transistor. How does it differ from p-n-) transistor?

Q.20. 25 watt and 100-watt bulbs are joined in series and connected to the main. Which bulb will glow brighter?

Q.21. How potentiometer is used to find out the internal resistance of given cell?

Q.22. A capacitor of 20 m F charged by 500 volt is connected in parallel with another capacitor of 10 m F charged by 200 V. Find the common potential.

Q.23. Explain the terms. (i) Ground wave (ii) Sky wave (iii) Space wave propagation.

Q.24. Copper has 8 x 1021 electrons per cubic meter. A copper wire of length lm and cross-sectional area 8 x 1 0-1 m2 carrying current and lying perpendicular to magnetic field of 5 x 10-1 T, experiences a force of 8 x 10-2 N. Calculate drift velocity of free electrons.

Q.25. Derive an expression for the frequency of radiations emitted by an atom while electron jump from higher energy level to the lower energy level.

Q.26. What is a junction transistor? Mention its two types. How are the', represented?

Q.27. Using Kirchhoff's laws in the given electrical network. Calculate the values of I1, I2&I3.

Q.28. A dielectric slab of thickness t (< d) is placed in a parallel plate capacitor. Derive an expression for the capacitance of capacitor . OR

What do you understand by dielectric polarization? Hence establish the relation K= 1 + X.

Q.29. Describe J.J. Thomson's experiment for determination of (e/m ) of cathode rays.

Q.30. A capacitor of 2m F and resistor of resistance 40 MW are joined in series through a key to a battery of 1 0 V. The key is closed at t = 0. Find the current and charge on the capacitor (i) at t = 0 and (ii) t = 20 s.



Fig1for Q.27