11886f.. ac circuits

8/12/2019 11886f.. Ac Circuits

1/5

http://www.cbseguess.com/

Guess Paper 2012Class XII

Subject Physics

ALTERNATING CURRENT AND ELECTRICAL MACHINES

1. A sinusoidal voltage V=200 sin 314t is applied to a resistor of 10 ohms resistance.Calculate (i) rms value of the voltage (ii) rms value of the current and (iii) po!erdissipated as heat in !atts.

2. An ideal inductor is in turn put across 220V "0 #$ and 220V 100 #$ supplies. %ill thecurrent flo!ing through it in the t!o cases &e the same or different'

3. %hat is the phase relationship &et!een the current flo!ing and the voltage applied inan ac circuit for a pure inductor'

4. A virtual current of 4 A flo!s in a coil !hen it is connected in a circuit having alternatingcurrent of freuenc "0 #$. *o!er consumed in the circuit is 240 %. Calculate theinductance of the coil if the virtual p.d. across it is 100 V.

5. An ac source + = +o ,int is applied across an inductor of inductance -. ,ho!mathematicall that the current lags &ehind voltage & phase angle of 2.

/. A capacitor is connected an ac source. f the freuenc of the source &e increasedho! does the current in the capacitor is affected'

. A coil has an inductance of 1 henr. (a) At !hat freuenc !ill it have a reactance of

3142 ohms' (&) %hat should &e the capacit of a capacitor !hich has the samereactance at that freuenc'

8. A 1f capacitor is connected to a 220 V "0 #$ ac source. Calculate the rms value ofthe current through the circuit. Also find the pea value of voltage across the capacitor.

. A capacitor C and a &ul& are connected in series to the ac mains as sho!n. 5he &ul&glo!s !ith some &rightness. #o! !ill the glo! of the &ul& change !hen a dielectricsla& is introduced &et!een the plates of the capcitor' 6ive reason in support of ourans!er.

10. An ac circuit consists of a 220 V "0 #$ suppl connected across a 100 ohms

resistance. %hat inductance should &e connected in the circuit in series !ith theresistance so that the current is reduced to half'

11. A 100 V "0 #$ ac source is connected to a series com&ination of an inductance of 100m# and a resistance of 2" ohms. Calculate the magnitude and phase of the current.

12. An 70 V 700 % heater is to &e operated on 100 V "0 #$ suppl. Calculate theinductance of the choe reuired.

13. %hat is the difference &et!een reactance and resistance' An electric lamp !hich runsat 70 V dc consumes 10 A current. 5he lamp is connected to 100 V "0 #$ ac source.

!!!.c&seguess.com

8ther +ducational *ortals!!!.icseguess.com 9 !!!.ignouguess.com 9 !!!.dulife.com 9 !!!.magicsense.com 9

!!!.niosguess.com 9 !!!.iitguess.com
http://www.cbseguess.com/http://var/www/apps/conversion/tmp/scratch_3/www.cbseguess.comhttp://var/www/apps/conversion/tmp/scratch_3/www.icseguess.com%20%7C%20www.ignouguess.com%20%7C%20www.dulife.com%20%7C%20www.magicsense.com%20%7C%20www.niosguess.com%20%7C%20www.iitguess.comhttp://var/www/apps/conversion/tmp/scratch_3/www.icseguess.com%20%7C%20www.ignouguess.com%20%7C%20www.dulife.com%20%7C%20www.magicsense.com%20%7C%20www.niosguess.com%20%7C%20www.iitguess.comhttp://var/www/apps/conversion/tmp/scratch_3/www.cbseguess.comhttp://var/www/apps/conversion/tmp/scratch_3/www.icseguess.com%20%7C%20www.ignouguess.com%20%7C%20www.dulife.com%20%7C%20www.magicsense.com%20%7C%20www.niosguess.com%20%7C%20www.iitguess.comhttp://var/www/apps/conversion/tmp/scratch_3/www.icseguess.com%20%7C%20www.ignouguess.com%20%7C%20www.dulife.com%20%7C%20www.magicsense.com%20%7C%20www.niosguess.com%20%7C%20www.iitguess.comhttp://www.cbseguess.com/

8/12/2019 11886f.. Ac Circuits

2/5


Calculate the inductance of the choe reuired.

14. A student connects a long air core coil of manganin !ire to a 100 V dc source andrecords a current of 1." A. %hen the same coil is connected across 100V "0 #$ acsource the current reduces to 1.0 A. (i) 6ive reasons for this o&servation and (ii)calculate the value of the reactance of the circuit.

1". An alternating voltage + = 200 sin 300t is applied across a series com&ination of : =10 ohms and an inductor of 700 m# inductance. Calculate (i) the impedance of thecircuit. (ii) *ea value of the current in the circuit and (iii) po!er factor of the circuit.

1/. %hen 100 V ;C is applied across an inductor a current of 1A flo!s through it. f thesame inductor is connected to a 100V AC source the current in the later reduces to 0."

A. %h is the current reduced in the later case' Calculate the value of the reactance ofthe inductor'

1. An air core coil and an electric &ul& are connected in series across a 220V "0 #$ acsource. 5he &ul& glo!s !ith some &rightness. #o! !ill the glo! of the &ul& &e affected!hen an iron rod is introduced into the coil '

17. An a.c. circuit having an inductor and a resistor in series dra!s a po!er of "/0 % froman a.c. source mared 210 V /0 #$. f the po!er factor of the circuit is 0.7 calculate (i)the impedance of the circuit and (ii) the inductance of the inductor used.

19. A &ul& of resistance 10 connected to an inductor of inductance - is in series !ith anac source mared 100 V "0 #$. f the phase angle &et!een the voltage and the

current is 4 radian calculate the value of -.

20.

8/12/2019 11886f.. Ac Circuits

3/5


Calculate the values of resistance and inductance.

2". An alternating current of 1." mA and angular freuenc 300 rads flo!s through a 10 ?ohms resistance and 0.0" micro@ farad capacitor in series. Calculate the value of rmsvoltage across the capacitor and the impedance of the circuit.

26. An ac circuit consists of a series com&ination of circuit elements and B. 5he current is

ahead of the voltage & phase 4. f the element is a pure resistor of 100 (i) namethe circuit element B and (ii) calculate the rms current if rms voltage is 141 V.

ASHISH SATAPATHY DPS DAMANJODI

27. n a series :@C circuit : = 30 and C = 0.2"

8/12/2019 11886f.. Ac Circuits

4/5


resistor (&) the capacitor (c) the inductor and (d) the complete circuit.

35. An inductor - a capacitor 20 f a resistor 10 are connected in series !ith an ac

source of freuenc "0 #$. f the current is in phase !ith the voltage calculate theinductance -

36. A "0 m# inductor a capacitor 20 f a resistor 10 are connected in series !ith an ac220 V source of varia&le freuenc. Calculate (i) the resonant freuenc of the circuit(ii) current amplitude at resonance and (iii) maimum po!er dissipation.

3. A circuit !ith : = 0 ohms in series !ith a parallel com&ination of - = 1." # and C = 30micro@farad is driven & a 230V suppl of angular freuenc 300 rads. (i) )10@2f !ill have to &e connected in the circuit to &ring itspo!er factor to unit.

41. A 2".0 micro@farad capacitor. A 0.1# inductor and a 2".0 ohms resistor are connectedin series !ith an ac source !hose emf is given & the euation + = 310 sin 314t. (i)

%hat is the freuenc of the emf' (ii) Calculate (a) the reactance of the circuit (&) theimpedance of the circuit and (c) the current in the circuit.

42. A capacitor a resistor and a 40m# inductor are connected in series to an ac source offreuenc /0#$.Calculate the capacitance of the capacitor if the current is in phase!ith the voltage.

43. Calculate the capacitance of the capacitor !hich !hen connected in series !ith aninductor of inductance 4 # !ill cause the circuit to resonate at "0 #$. .

44. A step@up transformer !ith 1"0 primar and 1"00 secondar turns !ors at "Eefficienc. 5he primar dra!s a current of 2." A !hen connected to an AC source of

220 V. Calculate the current and voltage from the secondar.

4". 5he output voltage of an ideal transformer connected to a 240 V AC mains is 24 V.%hen this transformer is used to light a &ul& !ith rating 24 V 24 % calculate thecurrent in the primar coil of the circuit.

46. A to!n is situated 20 m a!a from a po!er plant generating po!er at 440 V reuires/00 % of electric po!er at 220 V. 5he resistance of the t!o !ire lines carring po!er

is 0.4 per m. 5he to!n gets po!er from the line through a 3000@220 V step do!ntransformer at a su&station in the to!n. (i)

8/12/2019 11886f.. Ac Circuits

5/5


loss due to leaage'

Paper Submitted By:

Name: ASHIS KUMAR SATAPATHYEmai: a!"i!!atapat"y#$%&'(mai)*+mP"+,e N+) $-.%%$#/0-

!!!.c&seguess.com

8ther +ducational *ortals!!!.icseguess.com 9 !!!.ignouguess.com 9 !!!.dulife.com 9 !!!.magicsense.com 9

!!!.niosguess.com 9 !!!.iitguess.com
http://www.cbseguess.com/http://var/www/apps/conversion/tmp/scratch_3/www.cbseguess.comhttp://var/www/apps/conversion/tmp/scratch_3/www.icseguess.com%20%7C%20www.ignouguess.com%20%7C%20www.dulife.com%20%7C%20www.magicsense.com%20%7C%20www.niosguess.com%20%7C%20www.iitguess.comhttp://var/www/apps/conversion/tmp/scratch_3/www.icseguess.com%20%7C%20www.ignouguess.com%20%7C%20www.dulife.com%20%7C%20www.magicsense.com%20%7C%20www.niosguess.com%20%7C%20www.iitguess.comhttp://var/www/apps/conversion/tmp/scratch_3/www.cbseguess.comhttp://var/www/apps/conversion/tmp/scratch_3/www.icseguess.com%20%7C%20www.ignouguess.com%20%7C%20www.dulife.com%20%7C%20www.magicsense.com%20%7C%20www.niosguess.com%20%7C%20www.iitguess.comhttp://var/www/apps/conversion/tmp/scratch_3/www.icseguess.com%20%7C%20www.ignouguess.com%20%7C%20www.dulife.com%20%7C%20www.magicsense.com%20%7C%20www.niosguess.com%20%7C%20www.iitguess.comhttp://www.cbseguess.com/

11886f.. ac circuits

Documents