Electric Charges and Fields Flashcards
what is electrostatics
it is the study of forces, fields and potentials associated with static charges
what is frictional electricity
electricity developed on objects when they are rubbed with each other is called frictional electricity. Electric charges developed cannot move from one part of the object ot the other part and hence they are called static charges.
the bodies get charged and are hence said to be electrified
what causes objects to get charged when rubbed with one another
When 2 objects are rubbed together, the electrons from one object get transferred to the other object. The object which looses electrons becomes +vely charged while the object that gains electrons/ on which electrons get accumulated becomes -vely charged.
which body has more mass? +vely charged or -vely charged?
The +vely charged particle has lesser mass than original body due to the loss of electrons
the -vely charged body has more mass than original due to increase in no. of e-s
what is polarity
the property that differentiates between the 2 types of charges is called polarity. There are 2 types of charges +ve and -ve charge.
what is thecharge on
i) glass rod
ii) silk/wool
iii) ebonite rod/plastic/comb/amber
iv) cat fur/dry hair
i) +Ve
ii)-ve/+ve
iii)-ve
iv)+ve
what is the gold leaf electroscope
The gold leaf electroscope is a simple device that is used to detect the presence of charges.
It consists of a metal rod with 2 thin gold leaves attached to its end. The metal rod is placed in a glass jar fitted with an insulating cork, such that the gold leaves are present in the jar and a metal knob is present on the rod on the outer side of the jar.
expain the working of an electroscope
When a charged body is placed in contact with the mtal knob of an electroscope, the charge gets conducted through the metal rod into the 2 gold leaves.
Hence 2 gold leaves attain a similar charge, hence get repelled and diverge.
The digree of divergence is an indicator of the amount of charge. Greater the divergence, larger the magnitude of charge.
what happens when we touch the knob of an electrified electroscope
If we touch a +vely charged eelctroscope, electrons from the earth travel through us into the electroscope, causing he +Ve charge to be nullified. Hence it becomes neutral/discharged.
If we touch a -vely charged electroscope, electrons from the electroscope travel through us into the earth, causing a -ve charge to be nullified. Hence it becomes neutral/discharged.
differentiate between electric conductors and insulators
Conductors:
- materials which allow the flow of electricity through them
- they have electrons which are free to move in the material
- When some charge is transferred to it, it gets distrubuted all over the material
- eg: metals like copper a,luminium
Insulators:
- materials which offer high resitsnace to the passage of electricity through it,
- The electrons are so tighly bound that there is 0 electron flow through them
- When some charge is transferred to it, it remains localised in one place
-eg: platic, nylon, rubber,wood
what is earthing/ grounding
The process of sharing charged with the earth is called earthing/grounding.
When a charged body is kept in contact with the earth, all the excess charges on the body disappears through the connecting conductor
what are methods of chargng
i) conduction
ii) induction
describe charging by conduction
Charging by condcution involes contact of the uncharged body with the charged body and the same charge is produced on the neutral body.
When a +ve ly charged body is brought in contact with a ntueral body, eelctrons move from the neutral body to the +vely charged body and the neutral body becomes +vel charged.
Whne a -vely charged body is brought in contcat with a neutral body, electrons fro m the -vely charged body mov einto the neutral body and hence it becomes -velyc harged.
explain how to charge a pith ball +vely using induction
(or)
How can you charge a metal sphere positively without
touching it?
IMPORTANT: DRAW DIAGRAMS FOR EACH STEP. REFER TO TB.
i) A neutral sphere is placed on an insulating stand
ii) The -vely charged rod is brought near the sphere, the free electrons move away due to repulsion. The near end becomes +vely charged due to movement of electrons away from it and the opposite end becomes -vely charged eut to accumulation of electrons.
iii)Connect the sphere to the ground by a conducting
wire. The electrons will flow to the ground while the positive charges
at the near end will remain held there due to the attractive force of
the negative charges on the rod
iv) -vely charged rod is removed
v) +ve charge will spread uniformly over the metal sphere.
for -vely charging:
ii) A +vely charged rod is brought near the sphere, the free electrons move closer due to attraction, The near end becomes -vely charged due to accumulation of electrons. The opposite end becomes +vely charged due to loss of electrons
iii) Electrons from the earth move into the sphere via the conducting wire and neutralise the +ve charges on the opposite end. The -ve charges remain held there due to attractive force of +vely charged rod.
how to charge 2 spheres oppsitely
i) Take 2 neutral spheres placed on insulating stands. Place them such that they are in contact with each other.
ii) Bring a +vely charged rod near A, The free electrons from the spheres get transferred to the near end of sphere A due to attraction. The rear end of sphere B gets a +ve charge due to loss of electrons while near end of sphere A gets a -ve charge due to accumulation of electrons.
iii) Seperate the spheres by a small distance while holding the rod. The 2 spheres are oppositely charged and attract each other,
iv) Remove the rod. The charges rearrange themselves
v) Seperate the spheres quite apart. the charged rearrange themselves.
