Download Name: Batteries and EMF - Practice 1. A 100 W light bulb is plugged

Name: _______________________________
Batteries and EMF - Practice
1. A 100 W light bulb is plugged into a standard 120 V outlet.
A. How much does it cost per 31-day month to leave the light turned on continuously?
Assume electrical energy costs $0.12/kW·h.
B. What is the resistance of the bulb?
C. What is the current in the bulb?
2. A potential difference of 1.20 V will be applied to a 33.0 m length of 18-gauge copper wire
(diameter = 0.0400 in.). [Helpful info: Cu = 1.69 x 10-8  m 1.000 in = 2.540 cm]
A. Calculate the current.
B. Calculate the magnitude of the current density.
C. Calculate the magnitude of the electric field within the wire.
D. Calculate the rate at which thermal energy will appear in the wire.
3. The ideal batteries have emfs E1 = 12 V and E2 = 6.0 V. R1 = 4.0 
and R2 = 8.0 .
A. What is the current in the circuit?
B. What is the energy dissipation rate in resistor 1 (4.0 Ω)?
4. The ideal batteries have emfs E1 = 150 V and E2 = 50 V and the
resistances are R1 = 3.0 Ω and R2 = 2.0 Ω. If the potential at P
is 100 V, what is it at Q?
5. Five 5.00  resistors are connected as shown. Find the
equivalent resistance between points F and H.
6. The ideal batteries have emfs E1 = 10.0 V and E2 = 5.00 V, and
the resistances are each 4.00 Ω.
A. What is the current in resistor 2?
B. What is the current in resistor 3?
Solutions:
1. A. $8.93
2. A. 1.74 A
3. A. 0.50 A
4. -10 V
B. 144 
C. 0.833 A
6
2
B. 2.15 x 10 A/m
C. 3.64 x 10-2 V/m
B. 1.0 W
5. 2.50 
D. 2.09 W
6. A. 0.00 A
B. 1.25 A