Suppose that R:54 Ω Find the numerical value of RL Express your answer to three significant figures and include the appropriate units RL-Value Units Submit vio Figure Incorrect Try Again 4 attempts remaining Part B 30 0 Find the maximum power transferred to RI Express your answer to three significant figures and include the appropriate units 45 2 3. Suppose that R:54 Ω Find the numerical value of RL Express your answer to three significant figures and include the appropriate units RL-Value Units Submit vio Figure Incorrect Try Again 4 attempts remaining Part B 30 0 Find the maximum power transferred to RI Express your answer to three significant figures and include the appropriate units 45 2 3.6 kV(+ 300Ω L 150i 30Ω 15 Ω pmax = Value Units Submit Request Answer Problem 4.90 PSpicelMultisim Part A The variable resistor (RL.) in the circuit in (Figure 1) is adjusted for maximum power transfer to RI. When DR25 germanium diode is connected in reverse bias, it has a very high reverse resistance and it only conducts at more than 70 degree of room temperature.Problem 4.90 PSpicelMultisim Part A The variable resistor (RL.) in the circuit in (Figure 1) is adjusted for maximum power transfer to RI. We should also note that we can also build a Fire alarm circuit, using DR25 germanium diode, as it works as heat sensor. Now at this point, connect the thermistor again. Means from this point, if we decrease the resistance, even very little, Buzzer starts to beep. To do this remove the thermistor and let RV1 be the grounded, now adjust the value of RV1 to that point, where even slight turning of the RV1 starts the Buzzer. So we have to carefully adjust the value of Variable resistance RV1 and Thermistor, to make the circuit work properly. In transistor, usually 0.7v voltage is required across the Base and Emitter, to turn it ON. And when transistor becomes OFF, Reset pin of 555 timer IC, gets positive voltage through R3, and 555 IC starts to work and buzzer beeps. Now when we start heating the Thermistor through Fire, its resistance starts to decrease, and when its resistance decreases, the voltage at the base of Transistor starts to decrease and when the voltage becomes less than the operating voltage (base-emitter voltage V BE) of transistor, then transistor becomes OFF. When the Transistor is ON, Pin 4 (RESET) is connected to the Ground, and when Reset pin is Grounded, 555 IC doesn't operate. And transistor remains at ON state because there is sufficient voltage across the base-emitter of transistor, which makes it ON. When there is no FIRE, thermistor remains at 10k ohm. You can see the circuit diagram of fire alarm in above figure. You can find more such simple circuits here in this electronic circuits section. We have built the circuit using, mainly three components that is, Thermistor, NPN transistor and 555 Timer IC. Thermistor is temperature sensitive resistor, whose resistance changes according to the temperature, its resistance decreases with the increase in temperature and vice versa. The key component of the circuit is Thermistor, which has been used as fire detector or fire sensor. A variable resistor is used because a potential divider with 3 terminals is known as a potentiometer. A variable resistor is an electromechanical transducer that generally works by sliding a contact (wiper) over a resistive element. Here we are building one simple fire alarm system with the help of 555 Timer IC, which will sense the fire (temperature rise in surrounding), and trigger the alarm. A variable resistor is a resistor in which the electric resistance value is adjustable. It not only prevents a big losses caused by deadly fire but sometimes proves to be life savers. They detects the fire in ambiance at very early stage by sensing smoke or/and heat and raise an alarm which warns people about the fire and furnish sufficient time to take preventive measures. Fire alarms are prime necessities in modern buildings and architectures, especially in banks, data centers and gas stations.