Power Inverter

Correct Answer: Modified sine wave

The characteristic that best describes the output waveform of a typical power inverter used in laptop computers is a modified sine wave. Power inverters in laptops typically produce a modified sine wave output because: 1. It's cost-effective to produce compared to pure sine waves. 2. It's efficient for most electronic devices, including laptop components. 3. It provides a good balance between power quality and inverter complexity. The modified sine wave is a stepped waveform that approximates a sine wave, making it suitable for powering most electronic devices without causing significant issues. Regarding the other options: Pure sine wave with harmonic distortion is not typical for laptop power inverters. While pure sine waves are ideal, they are more expensive to produce and usually unnecessary for most laptop applications. Square wave with variable frequency is not commonly used in laptop power inverters. Square waves can cause issues with sensitive electronics and are generally considered lower quality than modified sine waves. Triangular wave with constant amplitude is not a typical output for laptop power inverters. This waveform is not commonly used in power conversion for electronic devices and would not provide the necessary power characteristics for laptop components.

Correct Answer: Check the inverter output with a multimeter

The best way to confirm the suspicion that the internal power inverter is faulty is to check the inverter output with a multimeter. The power inverter converts DC power from the laptop battery to AC power for the backlight of the LCD screen. If the inverter is not functioning properly, it will not provide the necessary voltage to power the screen, resulting in a dark display. By measuring the output of the inverter with a multimeter, the technician can determine if it is producing the correct voltage. If the output voltage is absent or significantly below the expected level, it confirms that the inverter is faulty and needs to be replaced. The other options, such as inspecting the motherboard visually, testing the AC adapter voltage, or disconnecting and reconnecting the battery, do not directly test the inverter and may not provide conclusive evidence of a faulty inverter.

Correct Answer: 200 watts

The technician should choose a 200-watt inverter to handle the power requirements. Here's why: When selecting an inverter, it's essential to consider not only the total wattage of the devices that need to be powered but also to account for potential power surges and provide some headroom for additional devices or future expansion. In this case, the devices require a total of 150 watts. Choosing an inverter with the exact same wattage (150 watts) would not be ideal because: 1. It leaves no room for power fluctuations or surges, which could damage the inverter or the connected devices. 2. It doesn't provide any extra capacity for adding more devices in the future or for devices that may require more power than their rated wattage during startup. A fictional 188-watt inverter, while higher than the required 150 watts, is still too close to the total power requirement and may not provide sufficient headroom. A 200-watt inverter is the best choice among the given options because: 1. It provides an additional 50 watts of headroom, which can accommodate power surges and fluctuations. 2. It allows for the possibility of connecting additional devices or devices with higher startup power requirements. The other options, such as 50 watts and 100 watts, are insufficient for the given power requirements. A 250-watt inverter would work but might be more than necessary for this specific situation.