current electricity

Question 1

the rate of flow of charge is called

Answer 1

electric current

Question 2

thermal speed of a electron

Answer 2

root3kT/m (m= mass of electron, T= temp in kelvin)

Question 3

chrge of electron

Answer 3

1.6 X 10^ -19 C

Question 4

acc of electron

Answer 4

-eE/m (E=V/L, E= potential diff, V= emf of battery, L= length of conductor )

Question 5

drift velocity

Answer 5

-eEτ/m (-eE/m = acc of electron)

Question 6

relaxtion time of electron (τ)

Answer 6

total time taken/ no of collisions

Question 7

relation between current and drift velocity

Answer 7

I= neA vd (n= no of free electrons, A= area of cross section, vd= drift velocity)

Question 8

current denisty

Answer 8

I= int J. dA

Question 9

relation between current density conductivity and electric field

Answer 9

J= ne^2 τ E/m

Question 10

slope of the V vs T graph gives

Answer 10

resistance

Question 11

temp affect on resistance

Answer 11

Rt= Ro(1+ alpha delta t) (Rt=resistance at t temp,R0= resistance at 0 c, delta t= increase in temp, alpha=temp coeff )

Question 12

resistivity

Answer 12

ρ= RA/l

Question 13

whats is called the balance point of wheatstone bridge

Answer 13

when Vc= Vd (current in R5= 0)

Question 14

whats the terminal voltage if the cell is discharging

Answer 14

V= E-Ir (E= emf of the cell, r= internal resistance of the cell, I= current)

Question 15

current formula in form of emf and resistance

Answer 15

I= E/r+R

Question 16

Greater the current drawn from the cell _____ is the terminal V

Answer 16

smaller

Question 17

whats the terminal voltage if the cell is discharging

Answer 17

V= E-Ir

Question 18

whats the terminal voltage if the cell is open circuit

Answer 18

V=E

Question 19

whats the terminal voltage if the cell is short circuited

Answer 19

V=0

Question 20

series combination of cells (current)

Answer 20

I= Enet/ rnet+ R (rnet= equivalent internal resistance, E net= equivalent emf )

Question 21

parallel combination of cells (if m identical cells are connected in parallel)

Answer 21

I=mE/mR+r

Question 22

the samll resistance connected in parallel to galvanometer coil in order to control current flowing through galvanometer is called

Answer 22

shunt resistance

Question 23

Conversion of galvanometer to ammeter (formula)

Answer 23

Rs= Rg X ig/ (i-ig) [Rg= resistance of the coil of galvanometer, ig= current req to achieve full scale deflection of the galvanometer, i= current in ammmeter]

Question 24

conversion of galvanometer to voltmeter

Answer 24

R= V/ig -Rg

Question 25

joules law of heating

Answer 25

I^2 Rt= V^2 t / R= V I t

Question 26

POWER formula

Answer 26

I^2 R= V^2/R= V I

Question 27

POWER formula in terms of emf and internal resistance

Answer 27

P= E^2R/ (r+R)^2

Question 28

when is P= P max

Answer 28

dP/dt= 0 or r= R

Question 29

Pmax formu;la

Answer 29

E^2/ 4R OR E^2/ 4 r

Question 30

power consumed if bulbs were in series

Answer 30

P total = P1 P2/ P1+P2

Question 31

power consumed if bulbs were in parallel

Answer 31

P total = P1+ P2

Question 32

if two heaters boils water in T1 and T2 what if both are connected in series then what would the total time taken to boil m kg of water

Answer 32

Ts = T1+ T2

Question 33

if two heaters boils water in T1 and T2 what if both are connected in parallel then what would the total time taken to boil m kg of water

Answer 33

Tp = T1 T2/ T1+T2

Question 34

fuse wire formulae

Answer 34

I^2 (ρl/ pi r^2) = H X 2pi rl

Question 35

charging of capacitor

Answer 35

q= eC (1-e^ - t/RC)

Question 36

discharging of capactor

Answer 36

q= q0 . e^ (-t/RC )

Question 37

current at any time t (charging C)

Answer 37

i= Ɛ/R X e ^ (-t/RC)

Question 38

voltage across C at time t (charging C)

Answer 38

V= Ɛ(1- e^(-t/RC))

Question 39

voltage across resistor(charging C)

Answer 39

Vr= 0.37 Ɛ

Question 40

heat generated(charging C)

Answer 40

1/2 X c Ɛ^2

Question 41

current in C during discharging

Answer 41

q0 X e ^ (-t/RC) / RC