Figure 1 shows a simplified structure of an N-channel enhancement mode MOSFET - AQA - A-Level Physics - Question 1 - 2021 - Paper 8

The correct terminal is the source.

For the lamp, the power can be calculated using the formula:

P = rac{V^2}{R}

where:

• P = 0.65 W
• R = 154 Ω.

From this, we can determine the voltage across the lamp:

I = rac{P}{V} = rac{0.65 ext{ W}}{154 ext{ Ω}} \\ \\ I ext{ is approximately } 4.23 ext{ mA}.

As stated, using the graph in Figure 2, we can observe that the minimum gate-source voltage, $V_{GS}$, required to allow this current when $V_{DS} = 12V$, would be between 3.4 V and 3.5 V.

To calculate the current consumption on standby from the mobile phone specifications, we can use the number of transistors and the individual current of about 10 nA per MOSFET.

Thus, the total current consumption can be approximated as:

$I_{ ext{total}} = 8.5 imes 10^9 imes 10 ext{ nA} = 8.5 ext{ mA}$

Given that the battery capacity is 3110 mA·h, we can find out how long the phone can last on standby:

ext{Time} = rac{ ext{Battery capacity (mAh)}}{I_{ ext{total}} (mA)} imes 60 ext{ min/h} = rac{3110}{8.5} imes 60 \\ ≈ 21.8 ext{ hours}.

This means that the phone can stay on standby for about 21.8 hours, which fits within the battery specification. This also suggests that the efficiency of using MOSFETs in the CPU contributes positively to battery life.