Chapter 3,4,5 Essay Questions

8/16/2019 Chapter 3,4,5 Essay Questions

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Chapter 4: Essay questions (Paper 2 section C)

1. The acceleration of a magnet that drops vertically into a solenoid is much smaller than

the gravitational acceleration. Explain the statement. (4m)

• Magnetic flux change in the solenoid• Induced current generates in the solenoid

• Direction of induced current alays flos in the direction to generate !agnetic pole to

oppose the pole of the falling !agnet"

• #herefore$ acceleration is loer

2. Explain how the electromagnet crane can be used to lift scrap metal. (4m)

Current flo through the solenoid$ !agnetic field is produced

• %oft iron core ill &e !agneti'ed

• #he scrap !etal attracted to the iron core

• o current flo soft iron de!agneti'ed or !etal scrap fall don

3. Most of our electric energy comes from hydroelectric power stations and thermal

power station. These power station are connected y cales to transmit electricity to

users in industries! offices! schools and houses. This system is called the national grid

networ". Explain riefly the importance of the national grid networ" system in

distriuting electric energy to the users. (4m)

• #he electrical supply is continuous$ although there is faulty in one of the poer

station

• #he electrical energy fro! other station is directed to the the affected areas

• #he electrical energy fro! other area is directed to the areas that need !ore energy

• #he oerall cost of production of electricity can &e reduced

4. #iagram shows the pattern of magnetic field formed when current flows in a coil. Explain why

the magnetic field strength is greater at the center compared to the edge. (4m)

• #he direction of the !agnetic field on theleft coil is anti cloc*ise

• #he direction of the !agnetic field on the right coil is cloc*ise

•

• the !agnetic fields in the !iddle of the coil are in the sa!e direction"• %o the !agnetic field ill &e stronger in the !iddle"



5. $sing the concept of the magnetic effect of an electric current! explain with the aid of

diagrams how forces are produced on a wire in the coil of direct current electric

motor% (4m)

• #he (!agnadur) !agnets produce a !agnetic field fro! north to south"

• #he current in the ire produces a !agnetic field"

• #he to !agnetic fields interact and for! a catapult field"

• #he !otor ill rotate due to the differences of force produce

6. Explain how the generator wor"s to produce direct current. (4µ)

• rotate the coil in cloc* ise direction• the coil cut across the !agnetic field

• current is induced in the coil

• the co!!utator change the direction in the coil so that the direction of current in

external circuit alays the sa!e"

&. Explain the wor"ing principle of a transformer. (4m)

• +hen a"c" oltage is supplied to pri!ary coil$ (alternating current ill flo) and

• the soft iron core is !agneti'ed"#he !agnet produced aries in !agnitude and

direction"• #his causes a changing !agnetic flux pass through the secondary coil"

• ,n induced e"!"f" across the secondary coil is produced

8. Explain the wor"ing principle of an electric ell. (4m)

• +hen the &ell is pressed$ a current flos in the coils of the electro!agnet$ causing the

electro!agnet to &e !agneti'ed

• #he !agneti'ed electro!agnet attracts the soft-iron ar!ature$ causing the ha!!er to

stri*e the gong"

• #he !oe!ent of the ar!ature &rea*s the circuit and causes the electro!agnet to lose

it !agnetis!"

• #he light spring pulls the ar!ature &ac*$ re!a*ing the contact and co!pleting the

circuit again"

• #he cycle is repeated so long as the &ell push is pressed and continuous ringing occurs"



Chapter 4: Electronics (Paper 2 section C)

1. Explain ho the green shado produced in the C./ screen0 (4m)

• 1 heater supply produced electron on it surface

• +hen 3 * poer supply are connected Cathode rayselectron acceleratel in a straight

line"

• Cathode rays carry *inetic energy and

• conerts to light energy hen they hit the screen "

2. Explain hy the &ul& light up at night" (4!)

• ,t night resistance 5D. increases

• 6E increases (higher than 7"8 for %i)

• I & increases and sitch on transistor

• Ic$ increases and lights up &ul&

Chapter 5: Radioactivity (Paper 2 Section C)1. .adioisotope %trontiu!-97 is used to !easure the thic*ness of paper in a paper industry

Explain ho %trontiu!-97 is used to !easure the thic*ness piece of paper0 (4m)

• Put the radioactie source opposite the detector

• Detector is connected to the thic*ness indicator

• Detector detect the reading of the changes in counts#hic*ness is !easured ith the

thic*ness indicator

• If the reading of the detector is less than the specified alue$ the thic*ness of the paper is too tic* ice ersa

2" uclear fission produces a chain reaction" Descri&e ho the chain reaction occurs in a

nuclear fission of an ato! of raniu!- 23;" (4!)

• eutron &o!&arded a uraniu! nucleus and produced three neutral neutron

• #he ne neutron &o!&arded a ne uraniu! nucleus

• <or eery reaction$ the neutrons produced ill generate a chain reaction

• Diagra! of chain reaction



3. 72.Explain ho radioisotopes can &e used to detect the location of the lea*age (4!)

• .adioisotope is in=ected into the pipe

• #he ater in the pipe flo ith the radioisotope

• >-M tu&e as detector is used to find the lea*age across the pipe• .eading on detector increases hen near a lea*age

Chapter 3,4,5 Essay Questions

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