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# physics questions, EMF urgent help need Watch

1. im having a lot of difficulty with this question, could anyone help? cheers!

HRW6 28-38P When the lights of an automobile are switched on, an ammeter in series with them reads 14.0 A and a voltmeter connected across them reads 14.4 V. See Fig. 28-39. When the electric starting motor is turned on, the ammeter reading drops to 6.11 A and the lights dim somewhat.

If the internal resistance of the battery is 0.0500 and that of the ammeter is negligible, what are

(a) the emf of the battery

here is a link to the picture.

http://www.webassign.net/hrw/hrw7_27-48.gif
2. (Original post by fabregassed)
im having a lot of difficulty with this question, could anyone help? cheers!

HRW6 28-38P When the lights of an automobile are switched on, an ammeter in series with them reads 14.0 A and a voltmeter connected across them reads 14.4 V. See Fig. 28-39. When the electric starting motor is turned on, the ammeter reading drops to 6.11 A and the lights dim somewhat.

If the internal resistance of the battery is 0.0500 and that of the ammeter is negligible, what are

(a) the emf of the battery

here is a link to the picture.

http://www.webassign.net/hrw/hrw7_27-48.gif
Well,the question seems confusing,though.I've tried it but i'm not much sure.
V=14.4V when connected with bulb.
I=14A
R=?
V=IR
or, 14.4=14 X R
R=1.02 ohm
E=IR + Ir
= 14(1.02 + 0.05)
=15.1 V Ans.
3. (Original post by TymfAfterDeath)
Well,the question seems confusing,though.I've tried it but i'm not much sure.
V=14.4V when connected with bulb.
I=14A
R=?
V=IR
or, 14.4=14 X R
R=1.02 ohm
E=IR + Ir
= 14(1.02 + 0.05)
=15.1 V Ans.

thanks! its right
4. My pleasure.
5. I had this same problem. I realize it's almost a year later, but does anyone know how to find the current through the starting motor?

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