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Wednesday, July 4, 2012

DisaSter MaNaGeMent Assignment 1

1)What is Tsunami?
A)Tsunami is a series of water waves caused by the displacement of a large volume of a body of water, typically an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions (including detonations of underwater nuclear devices), landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami.
Tsunami waves do not resemble normal sea waves, because their wavelength is far longer. Rather than appearing as a breaking wave, a tsunami may instead initially resemble a rapidly rising tide, and for this reason they are often referred to as tidal waves. Tsunamis generally consist of a series of waves with periods ranging from minutes to hours, arriving in a so-called "wave train". Wave heights of tens of metres can be generated by large events. Although the impact of tsunamis is limited to coastal areas, their destructive power can be enormous and they can affect entire ocean basins; the 2004 Indian Ocean tsunami was among the deadliest natural disasters in human history with over 230,000 people killed in 14 countries bordering the Indian Ocean.

2) What are its reasons?
a)Tsunamis are caused by sudden movements of the earth that happens under the sea. Often the most destructive Tsunamis are caused by earthquakes but causes can also include volcanic eruptions, landslides or even a comet hitting the sea.
Landslides cause tsunamis when the debris falls into the water. This has the same effect of dropping a large stone into a pool - big ripples are created. But when this happens in the sea and it is thousands of tonnes of rock and earth falling into the sea a very large ripple, more like a tidal wave is created. This travels across the sea until it comes into contact with land and a tsunami is formed.
Volcanoes cause tsunamis when there is an eruption. The volcano can either be on land or under the sea, in which case it is known as a submarine volcano. If the volcanic eruption happens on land, the tsunami is caused by debris and lava from the volcano flowing into the sea, which once again causes a bug ripple.
If the eruption happens under water, the enormous power of the eruption sends shudders through the earth and disrupts the water. The water in the sea then breaks into waves which travel across the ocean until they come into contact with a coast. Here, a tsunami is formed.

3)How Can we Manage Tsunami without much risk?
a) Unfortunately nothing can be done to prevent Tsunamis. However, there are several organisations that use complex technology to monitor movement of the earths plates and sudden changes in water movement. There are also warning and evacuation procedures in place around countries like Japan and Hawaii where Tsunamis are frequent.
Any sudden earthquake that happens underwater will be detected in the same manner of on on-shore earthquake. These are measured in the Richter scale. If this is recorded then warning systems can sometimes be activated to evacuate people.

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Tuesday, July 3, 2012

Physics Class X Electricity Imp. Question

Very short answer questions (1 mark) 1. Give the unit of (a) Charge (b) Current
2. Define current
3. Name the unit of (a) electrical resistance (b) resistivity
4. Define One Ohm
5. Define Resistivity
6. What is the resistance of a torch bulb rated at 2.5 V and 500 mA?
7. Two resistances of each 2 ohm are connected in parallel. Find their equalent resistance.
8. On what factors does the resistivity of a material depend?
9. Plot a graph between the Potential difference V and current I through a conductor
10. What happens to the resistance of the circuit if the current through it is doubled?
Short answer questions (2 marks)
1. Two wires of same material are having length L and 2L. Compare their resistance and resistivity.
2. Why are coils of electric toaster and electric iron made of an alloy rather then a pure metal?
3. Two wires are of same length and radius but one of them is copper and the other is of iron. Which will have more resistance? (Given the resistivity of copper = 1.62 x 10 -8 ohm meter and resistivity of iron = 10 x 10-8 ohm meter.
4. Define 1KWh. Give the relation between 1kwh and Joule.
5. State which has a higher resistance. A 50W or 25W lamp. Also find the ratio of their resistances.
6. A wire of resistance 5 Ohm is spent in the form of closed circle. What is the resistance between 2 points at the ends of any diameter of the circle?
7. Calculate the amount of charge that would flow in one hour through the element of an electric iron drawing a current of 0.4 amps.
8. A electric toaster of resistance 20 Ohm takes a current of 5A. Calculate the heat developed in 30 s.
9. A bulb is rated at 5V, 100mA. Calculate its (1) Power (2) Resistance
10. Name two special characteristics of a heater coil.
Short answer questions (3 marks)
1. Define resistance and resistivity. Give the relation between them. Explain the dependence of resistance on temperature.
2. With the help of neat circuit, derive the expression for the equalent resistance of 3 resistances connected in series.
3. With the help of neat circuit, derive the expression for the equivalent resistance of 3 resistances connected in parallel
4. (a ) Draw the circuit consisting of a battery of five 2V cells, 5ohm resistor, 10 ohm resistor, 15 ohm resistor and a plug key. All connected in series (b) Calculate the current passing through the above circuit when key is closed.
5. Two identical resistors each of resistance 2 Ohm are connected in turn (1) in series (2) in parallel to a battery of 12 V. Calculate the ratio of power consumed in two cases.
6. A piece of wire is redrawn by pulling it until its length is tripled. Compare the new resistance with the original value.
7. An electric kettle is rated 500W, 200V. IT is used to heat 400 gm of water for 30 secs. Assuming the voltage to be 220V calculate the rise in temperature of water. Specific heat capacity of water is 4200 J/Kg ÂșC.
8. In an experiment the current flowing through a resistor and potential difference across it are measured. The values are given below. Show that these values confirm Ohm’s Law and also find the resistance of the resistor.
I (ampere) I(ampere) 1.0 1.0 2 1.5 2.0 2.0 2.5 2.5 3.0 3.0
V (volt) V(volt) 4.0 4.0 6.0 6.0 8.0 8.0 10.0 10.0 12.0 12.0
9. A heater draws 1100 W at 220V. (a) Find the resistance of the heater (b) Calculate the energy in KWh consumed in a week if the heater is used daily for 4 hours.
Long Answer questions (5 marks)
1. State Ohms law with a neat circuit. Explain how this law can be verified and also plot the expected v-I graph.
2. (a) Differentiate resistance and resistivity
(b) the ratio of resistivities of two materials a and b is 1:2, ratio of their length is 3:4 and if the ratio of radii is 2:3 find the ratio of resistance of a and b.