Thermal and Electrical Energies

Specific Heat uses the unit [J/(kg * ^◦C)]. Copper has a specific heat of 385, Gold at 129, Lead at 130, Tin at 227 and Zinc at 388. A 2-kg block of which material would require about 450 joules of thermal energy to increase its temperature by 1^◦C?

• Tin

• Zinc

• Gold

• Lead

Which material would require the most heat to raise a 5-kg sample of the material from 10^◦C to 50^◦C?

• Gold

• Lead

• Tin

• Zinc

How much Thermal Energy is needed to raise the temperature of 4.0 kg of water from 25^◦C to 75^◦C?1

• 840,000 J

• 800,000 J

• 84,000 J

• 8,400,000 J

The temperature of a 24.5-g block of aluminum decreases from 30.0^◦C to 21.5^◦C. If the aluminum has a specific heat of 897 J/(kg * ^◦C)], how large is the change in thermal energy of the block of aluminum?

• 187 J

• 2,590 J

• 5,820 J

• 187,000 J

Picture a closed circuit with one lightbulb, lightbulb A with a resistance of 8 ohm's, running in parallel series to lightbulb B, lightbulb B has a resistance of 15 ohm's and the entire circuit is running on a 12 V battery. What is the current of lightbulb B?

• 1.25 A

• 0.67 A

• 0.80 A

• 1.5 A

The current through a lightbulb is 2.5 A. The lamp is connected to a battery supplying a voltage difference of 12 V. What is the power of the lightbulb?

• 15 W

• 30 W

• 26 W

• 14.5 W

A person spends four hours a day in a room but leaves a 100-W lightbulb on 24 hours a day. How much electrical energy would be saved if the bulb was on for only the four hours that the person was in the room?

• 1 kWh

• 3kWh

• 4kWh

• 2kWh

If a closed circuit has a battery of 12 V, 3 lightbulbs and a current of 1.0 A, what is the total resistance of the circuit?

• 12 ohms

• 9 ohms

• 6 ohms

• none of the above

A toy car with a resistance of 20 ohms is connected ta 3-V battery. What is the current in the car?

• 3 A

• 6.7 A

• 60 A

• 0.80 A

A calculator uses a 9 V batter and draws 0.1 A of current. What is the power of the calculator?

• 0.9 W

• 9.0 W

• 90 W

• 0.009 W