Name Chapter 34 Electric Current Calculating Power Class Date If four 1.5-V batteries deliver 1.25-A current to a small motor, what is the power provided to the motor? 1. Read and Understand What information are you given? voltage = V = 4 x 1.5 V = 6.0 V current=I= 1.25 A 2. Plan and Solve What unknown are you trying to calculate? power = P= ? What mathematical expression can you use to calculate the unknown? P = VI P= (6.0 V)(1.25 A) = 7.5 W 3. Look Back and Check Is your answer reasonable? Yes, the number calculated is a product of current and voltage and the units indicate power. Math Practice woy m On a separate sheet of paper, solve the following problems. 1. An 8.0-V power supply delivers a 1.75-A current to a circuit. Calculate the power provided to the circuit.

. All of the electrical outlets in a room are connected in a single parallel circuit (Figure 7.38). The circuit is equipped with a 20-A fuse, and the voltage is 120 V. (a) What is the maximum total power that can be supplied by the outlets without blowing the fuse? (b) How many 1,200-W appliances can be plugged into the sockets without blowing the fuse?

(Indicates a review question, which means it requires only a basic understanding of the material to answer. Questions without this designation typically require integrating or extending the concepts presented thus far.) . Six resistors, all having the same temperatures and compositions, are each attached to a battery with voltage V to form a simple circuit. The resistors have different lengths, l, but the same diameters. Rank the circuits according to the current that flows through the resistor from smallest to greatest. If two (or more) circuits have the same current flowing, give them the same ranking. Explain the rationale you used to establish your rankings. Circuit 1: l = 2 cm; V = 3 V Circuit 2: l = 2 cm; V = 6 V Circuit 3: l = 1 cm; V = 3 V Circuit 4: l = 1 cm; V = 6 V Circuit 5: l = 3cm; V = 2 V Circuit 6: l = 3cm; V = 6 V

A student in a physics lab mistakenly wired a light bulb, battery, and switch as shown in Figure 21.44. Explain why the bulb is on when the switch is open, and off when the switch is closed. (Do not try this-it is hard on the battery!)