Final answer:
The power used by the laptop screen is 8.0 W, calculated by taking the difference in power consumption with the screen off and on at full brightness. Circuit elements that dissipate power are resistors.
Step-by-step explanation:
Power Consumption of a Laptop Screen
To calculate the power consumed by the laptop screen, you would use the formula for electrical power, which is P = IV, where P represents power in watts, I represents current in amperes, and V represents voltage in volts. When the screen is off, the laptop draws 0.40 A of current, and when the screen is on at full brightness, it draws 0.90 A of current, with the DC power supply delivering 16 V.
The additional power consumed by the screen when it's on can be calculated as follows:
- Power with the screen off: Poff = Ioff × V = 0.40 A × 16 V = 6.4 W
- Power with the screen on: Pon = Ion × V = 0.90 A × 16 V = 14.4 W
- The power used by the screen alone: Pscreen = Pon - Poff = 14.4 W - 6.4 W = 8.0 W
The correct answer is that the power used by the screen is 8.0 W.
Circuit Elements
Regarding the circuit elements that dissipate power, the correct answer is resistors. Capacitors and inductors do not dissipate power in the ideal sense because they store energy temporarily in the electric field and magnetic field, respectively. Ideal switches are also not power dissipating elements because they are considered to have no resistance when closed and infinite resistance when open.