Q15 of 216 Page 465

i. Explain an activity to show that a current-carrying conductor experiences a force when placed in a magnetic field.

ii. State the rule which gives the direction of force acting on the conductor.

i. Force on a current carrying conductor placed in a magnetic field



French scientist Andre Marie Ampere (1775–1836) suggested that when a current-carrying conductor is placed in a magnetic field it will experience a force. The force due to a magnetic field acting on a current-carrying conductor can be demonstrated through the following activity.


1.Take a small metal (preferable aluminium) rod AB of about 5-10 cm in length. Using two connecting wires suspend it horizontally from a stand, as shown in the diagram.


2.Place a strong horse-shoe magnet in such a way that the rod lies between the two poles with the magnetic field directed upwards. For this put the north pole of the magnet vertically below and south pole vertically above the rod.


3. Connect the rod in series with a battery, a key, and a rheostat.


4. Press the key ‘k’ to let the current flow through the rod.


Observations - It is observed that the rod is displaced towards the left. Reversing the direction of current flowing (by changing the polarity of the battery) through the rod, it is observed that the direction of its displacement of the rod is now towards the right. The displacement of the rod in the above activity suggests that a force is exerted on the current-carrying rod when it is placed in a magnetic field. It also suggests that the direction of force is also reversed when the direction of current through the conductor is reversed.


ii. Fleming’s Left-Hand Rule


Fleming’s left-hand rule states that when you stretch the thumb, forefinger and middle finger of your left hand such that they are mutually perpendicular and if the first finger points in the direction of magnetic field and the second finger in the direction of current, then the thumb will point in the direction of motion or the force acting on the conductor.


More from this chapter

All 216 →
13

An object 4 cm in height, is placed at 15 cm in front of a concave mirror of focal length 10 cm. At what distance from the mirror should a screen be placed to obtain a sharp image of the object. Calculate the height of the image.

OR


At what distance form a concave lens of focal length 20cm a 6cm tall object be placed so as to obtain its image at 15cm from the lens? Also calculate the size of the image formed. Draw a ray diagram to justify your answer for the above situation and label it.

 14

i. Calculate the resistance of an electric bulb which allows a 10A current when connected to a 220 V power source.

ii. Draw a schematic diagram of an resistance of an electric circuit consisting of a battery of two cells each of 1.5 V, 5 Ω, 10Ω and 15Ω resistors and a plug key, all connected in series.

 16

i. Giving one example of each, explain how the following metals are obtained from their compounds by the process of reduction.

a. Meta ‘A’ which is low in the activity series of metals.


b. Metal ‘B’ which is in the middle of the activity series of metals.


ii. What is meant by refining of metals? In the electrolytic refining of metal M, name the cathode, anode and the electrolyte.

 17

An organic compound A having molecular formula C2H4O2 reacts with sodium metal and evolves a gas B which readily catches fire. An also reacts with ethanol in the presentce of conc H2SO4 TO form sweet smelling substance C used in making perfumes.

i. Identify the compounds A, B, and C and write their names.


ii. Write balanced chemical equations of represent conversion of


a. compound A into compound B


b. compound A into compound C


iii. Write the chemical composition of detergents. Mention their advantage over soaps for washing clothes.


OR


i. What are hydrocarbons? Give one example. with two examples each.


ii. Give the structural differences between started and unsaturated hydrocarbons


iii. What is a functional group? Give examples of two different functional group.