Page 320 - Schaum's Outline of Theory and Problems of Applied Physics

CHAP. 25] DIRECT-CURRENTCIRCUITS 305

Fig. 25-14 Fig. 25-15

Fig. 25-16

25.13. Two batteries in parallel, each of emf 10 V and internal resistance 0.5 , are connected to an external 20- resistor.
Find the current in the external resistor.
25.14. A dry cell has an emf of 1.5 V and an internal resistance of 0.08 .(a) Find the current when the cell’s terminals
are connected together. (b) Find the current when the cell is connected to a 5- resistance.

25.15. A certain “12-V” storage battery actually has an emf of 13.2 V and an internal resistance of 0.01 . What is the
terminal voltage of the battery when it delivers 80 A to the starter motor of a car engine?

25.16. A current of 2.2 A flows when a battery of emf 24 V is connected to a 10- load. Find (a) the internal resistance of
the battery and (b) its terminal voltage.

25.17. Two 12-V batteries, one with an internal resistance of 0.05 and the other with an internal resistance of 0.15 , are
connected in parallel with a load of 0.5 . Find the current in the load.

25.18. The batteries of Prob. 25.17 are connected in series with the same load. Find the current in the load now.

25.19. A generator whose emf is 240 V has a terminal voltage of 220 V when it delivers a current of 50 A. (a) Find the
internal resistance of the generator. (b) Find the power supplied by the generator. (c) Find the power dissipated
within the generator.

25.20. A storage battery of emf 34 V and internal resistance 0.1 is to be charged at a rate of 20 A from a 110-V source.
What series resistance is needed in the circuit?

25.21. Find the currents in the resistors of the circuit shown in Fig. 25-17. The internal resistances of the emf sources are
included in the external resistances.
25.22. Find the current in the resistors of the circuit shown in Fig. 25-18. The internal resistances of the emf sources must
be taken into account.

25.23. Find the currents in the resistors of the circuit shown in Fig. 25-19. The internal resistances of the emf sources are
included in the external resistances.