Magnetic Effects of Current HOTS Flashcards
who was oersted? what did he discover?
Hans Christian Oersted, one of the leading scientists of the 19th
century, played a crucial role in understanding electromagnetism.
In 1820 he accidentally discovered that a compass needle got deflected
when an electric current passed through a metallic wire placed nearby.
Through this observation Oersted showed that electricity and
magnetism were related phenomena.
how does oersted’s discovery help us
His research later created
technologies such as the radio, television and fiber optics. The unit of
magnetic field strength is named the Oersted in his honou.
why do we use a think wire for oersted’s experiment
a thin wire would not be suitable as we require a large amount of current to pass through the conductor to produce a good magnetic field.
whatis the other name of right hand thumb rule
This rule is also called Maxwell’s corkscrew rule. If we consider ourselves driving a
corkscrew in the direction of the current, then the direction of the corkscrew is the
direction of the magnetic field.
what are unifrom and non uniform magnetic fields
i) magnetic field lines are said to be unifrom if its magnitude is equal and direction is same at every point in a given space,
respresnted by parallel quidistant lines,
source:earth mag field/solenoid/bar magnet
ii) magnetic field is said to be non-uniform if its magnitude is not equal and direction is not same at every point in a given space.
source:mag field produced around a charhed particle when it enters into an external mag field
uses of electromagnet
i) it is used to lift heavy pieces of iron. fitted in cranes lifting heavy obj made of scrap iron
ii) used in many devices like electric bell, electric relay, telephone receiver etc,
iii)used to remove bullet,iron,splinters from human body
what are the factors in which the force acting in a current cuondoctor placed ⊥ to B depend
i) It is directly proportional to srength of magnetic field
ii) Directly proportional to amount fo current through conductor
iii) directly prportional to length of conductor
F=B I 𝓁
disadvantages of ac
- it is more changerous than dc
-cannot be used for electrolysis
who is responsible for elecricity supply to our homes
Electricity board of state is responsible for power supply to our homes and facories. The elextric power is supplied either through the underground cables or overhiead wires in poles
why is it important that the insulation of live wires should be thick
The insulation of wires should be thick so that when the wire gets heating due to a large amount of current, the insulation does not melt and expose the wire.
explain the importance of rating with respect to a fuse
We must always a fuse wire of correct rating. if we use a fue of rating higher than the required amount, then the fuse wire will not melt even when a large amount of current than permissible limit passes through it. Hence it will not act as a safety device.
why is the earth pin made thicker or longer in three pin plugs?
The ‘three pin plugs’, has three pins which are the live pin, neutral pin and the earth pin.
Among these three pins (live, neutral and earth), the earth pin is made longer and thicker than the other two pins, so that when we insert the plug into the socket, the earth pin comes into contact with the power supply before the other two pins, this is because if any unwanted charges are there then they will be removed (grounded) before the other two pins will go inside the terminals.
This will ensure that if we connect the earth first then that will increase our safety and the device’s safety if any fault occurs.
Also, the earth pin is made thicker so that even by mistake also it cannot be inserted into the holes for the live or neutral connection of the socket.
describe an experiment to show the working of a fuse?
i)take a set up with an aluminium of wire, say 5cm in light. Fix its two ends on the tips of the iron nails placed vertically on the table. Connect the iron nails, to a battery,key and a bulb
ii)Initially when key is plugged. current starts flowing. The bubl starts glowing brightly due to the flow of fast current. However soon the aluminium wire melts and breaks the circuit due to the heating effect of fast current.
what are the sources of AC Dc
AC - AC generator
Car alternator
dc-dry cell
mercury cell
voltaic cell
car storage battery
solar cell
dc generator
what are adv of dc and disadv of dc?
adv
->mainly produced in cell so it is compact
->can be used for electrolysis
->instant electrical energy
diadv
-cannot be transmitted over longer ditances
-> iincase of cells when the chemical reacn within the cell stops, the electrical energy also stops
differenciate between ac and dc
DC
->current flows in one fixed direction
>magnitude of current remains same
->the polarity is fixed
-> frequency is 0
AC
->current changes its direction in fixed intervals of time
->magnitude of current changes with every half a rotation
->its polarity is not fixed
-> ithas a defined frequency
what is frequency
f=1/T
T=2 x t
T=time period
what is ac frequency and voltage supply in usa and ksa
60hz/ 110V
What is the principle of transformer?
It is a device which changes Small ac potential difference to a larger ac potential difference. It allows for the transmission of ac current through conductors over longer distances without much loss of electrical energy or power
give energy conversions in the following:
->motor
->dynamo/generator
->battery/cell/inverter
->solar cell
->fuel cell or spaceship
i) electrical->mechanicla’
ii)mechanical->electrical
iii)chemical->electrical
redox reacn in cell, the chemical energy is converted to electrial enegry
iv)light->electrical
v)heat(combustionf fuel)->electrical
what happens if fuse is connected to neutral wire
i)if the fuse wire blows due to excess current, appliance stops but live wire still has high potential.
ii) so we will get sever shock if we touch it
sparrow on live wire does not burn but man touches live wire gets a sever shocl
i)sparrow stands only on the live wire. So there is no potential difference so no current flows
ii)but when man is standing of the ground(earth potential is 0) there i a potential difference 220-0 so current flows through him causing a shock
mag field of a solenoid depends upon?
-> directlr proportional number of turns
-> directly proportional amonto f current
->if pure soft iron core is used, the mag field is increased several times
new colours of wires
live-maroon
neutral- blue
earth-yellow
Under what conditions permanent electromagnet is obtained if a
current carrying solenoid is used?
i) direct current flows through solenoid
ii) steel rod is placed inside solenoid
how can we prevent overloading
- An excess number of devices should not be connected to the same socket.
- Multiple high power consumption devices should not be connected at the same time.
- The insulation of live wire and neutral wire must be thick and checked regularly.
