Electricity 3 Flashcards
define equivalent/ effective resistance
the resistance of series or parallel combination of resistors is equivalent resistors.
define resistors connnected in series?
two or more resistors are said to be connected in series if they are connected one after another in such a way that the same current flows through each of the resistor when a potential difference is applied across the ends of the combination of resistors.
effective resistance of a series combination of resistors rfers to sum of the individual resistance of the resistors connected inthe combination.
Rs= R1+R2+R3
what are the feautures of resistors connected in serieS?
i) the net resistance is equal to the sum of resistance of individual resistors.
ii)t the same current flows through each of the individual resistor.
iii) the potential difference across the ends of the combination of resistors is equal to the sum of potential difference across each individual resistor.
what are the disadvantages of resistors in series
i) series arrangement of electrical applicances is not used in household electric circuit. This is because if any one of the appliance fuses the rest will also stop working because there is onlyone path for the flow of current throguh all applicances.
ii) different applicances have different resistances and therefore will require different amounts of current to operate properly. In a series arrangement eveyr appiance gets equal current and therefore will not work properly.
define resistors connected in parallel
two or more resistors are said tobe connected in parallel if the one of eahc resistor is connected at one common point and the other end of each resistor is connected at another point such that the potential difference across each of the conductors is equalt ot he applied potential difference across the combination of resistors.
1/Rp= 1/R1+1/R2+1/R3
features of parallel combination of reistors
the sum of the reciprocal of the individual resistance of each of the resistors is equal to the reciprocal of net resistance.
-different amount of current flows through each resisitor.
a large amt of current flows through the resistor with least resistance. and a small amt through resistor with highet resistance
the sum of the current flowing through each individual resistor is eqal to the current flowing through the combinatin of resistors
-the potential difference across each of the resistors is equal to the voltage applied across the parallel combination of resistors.
what are the advantages of connectingelectricalappliances inparallel
i) if any one of the appliances fails, the others will still work properly and will not be affected.
ii) when the different electrical devices are connected in parallel, the potential difference across the ends of each device is equal to the applied potential difference and hence they draw current as per their requirement and work properly.
iii) since all appliances draws acc to needs there is no wastage of elecitrical enegry.
differentiate between resistors in series and parallel
series:
i) the I remains the same. All of them get total I
ii) The voltage gets divided acc to resistance.
iii)V=V1+V2+V3
iv)Vind=I tot and Rind
parallel:
i) The v remains constant, All fo them get same V as batteyr
ii) The I gets divided acc to resistance.
iii) I=I1 +I2+I3
iv) Vtot= I ind x R ind
ammeter is alway connected in series. why?
Ammeter is a low resistance device. An ideal ammeter has 0 resistance. If it is connected in parallel, it withdraws maximum amt of current flowing in a circuit. Due to the heating effect of current, it makes the instrument likely to burn
voltmeter is always connected in parallel. why?
Voltmeter is a high resistance device, It is used to measure voltage so it is connected in parallel since in parallel both components experience same voltage. If connected in series, it will change the value of potential differnce, minimize the current and give faulty reading.
if it were connected in series it would incrase the resistance to nearly infinite and no current would flow through it
