- #1
QueenFisher
I have this circuits question that I've tried to do, but I'm not sure about my answers and I'm sure I'm going wrong somewhere...
The 4.00 V cell in the circuits below has zero internal resistance. An accurately calibrated voltmeter across XY reads 1.50 V
http://home.ripway.com/2005-7/361234/circiut.bmp
a) Calculate the resistance of the voltmeter.
i did this :
Vyz = 1.5 V
therefore Vxy=4.00-1.50=2.50V
Ixy=Vxy/Rxy
=2.5/60
=0.041666666...
therefore Is=0.041666... (supply current)
I(40 ohm resistor)=V(40 ohm resistor)/R(40 ohm resistor)
=1.5/40
=0.0375
therefore Ivoltmeter=0.041666...-0.0375
=0.00416666...
1/Req=1/40 + 1/R(voltmeter)
=(Rv+40)/40Rv
Req=40Rv/(Rv=40)
Vs=Is x R(total)
R(total)=60+ ( 40Rv/(Rv+40) )
4.00=0.04166666... x 60+ ( 40Rv/(Rv+40) )
96=60+ ( 40Rv/(Rv+40) )
36=40Rv/(Rv+40)
36Rv+1440=40Rv
4Rv=1440
Rv=360
Voltmeter resistance=360 Ohms
This seem way too low for a decent voltmeter, so i think it's wrong, but i can't see how!
and for part b): Calculate the voltmeter reading when it is connected across Y'Z'
I did this:
1/Req=1/400 + 1/360
=19/3600
Req=189.473...
R(total)=189.473...+600
=789.473...
Is=Vs/R(total)
=0.0050666...
V(600 ohm resistor)=Is x R(600 ohm resistor)
=3.04V
V(400 ohm resistor)=Vs - V(600 ohm resistor)
=o.96
Voltmeter reads 0.960V
this seems so wrong!
i have no idea!
please help
The 4.00 V cell in the circuits below has zero internal resistance. An accurately calibrated voltmeter across XY reads 1.50 V
http://home.ripway.com/2005-7/361234/circiut.bmp
a) Calculate the resistance of the voltmeter.
i did this :
Vyz = 1.5 V
therefore Vxy=4.00-1.50=2.50V
Ixy=Vxy/Rxy
=2.5/60
=0.041666666...
therefore Is=0.041666... (supply current)
I(40 ohm resistor)=V(40 ohm resistor)/R(40 ohm resistor)
=1.5/40
=0.0375
therefore Ivoltmeter=0.041666...-0.0375
=0.00416666...
1/Req=1/40 + 1/R(voltmeter)
=(Rv+40)/40Rv
Req=40Rv/(Rv=40)
Vs=Is x R(total)
R(total)=60+ ( 40Rv/(Rv+40) )
4.00=0.04166666... x 60+ ( 40Rv/(Rv+40) )
96=60+ ( 40Rv/(Rv+40) )
36=40Rv/(Rv+40)
36Rv+1440=40Rv
4Rv=1440
Rv=360
Voltmeter resistance=360 Ohms
This seem way too low for a decent voltmeter, so i think it's wrong, but i can't see how!
and for part b): Calculate the voltmeter reading when it is connected across Y'Z'
I did this:
1/Req=1/400 + 1/360
=19/3600
Req=189.473...
R(total)=189.473...+600
=789.473...
Is=Vs/R(total)
=0.0050666...
V(600 ohm resistor)=Is x R(600 ohm resistor)
=3.04V
V(400 ohm resistor)=Vs - V(600 ohm resistor)
=o.96
Voltmeter reads 0.960V
this seems so wrong!
i have no idea!
please help