As resistance increases, 150 Ω electrons will lose more 4V This circuit could turn (a) energy as they pass 8 V on a fan when a through the resistor. 0 V computer overheats. Therefore, the voltage 12 V across the resistor will As the temperature increase. (a) 700 increases, the Ω 3.5 V resistance of the (a) 125 2.5 V thermistor decreases. Ω 225 3 V The voltage across the Ω 1.2 kΩ 100 °C thermistor decreases and the voltage across (a) 250 (a) 6 V R1 increases. Ω 300 2.5 V When this voltage Ω 40 0.016 A reaches 0.7 V, the Ω transistor switches on (a) 3 V (a) (NPN) Transistor and the LED lights. 3V As the temperature 0.5 V increases, the resistance of the (a) 3.8 V thermistor decreases. 1.0 V The voltage across the 0.6 V thermistor decreases and the voltage across (a) V1 = 6 V, V2 = 6 V R1 increases. V1 = 4 V, V2 = 10 V When this voltage V1 = 7 V, V2 = 3 V reaches 0.7 V, the V1 = 16 V, V2 = 6 V transistor switches on V1 = 4.5 V, V2 = 13.5 V and the LED lights. V1 = 5.5 V, V2 = 3 V Swap the positions of the thermistor and R1. (a) MOSFET As brightness of light decreases, the resistance of the LDR increases. The voltage across the LDR increases. When this reaches a high enough voltage, the MOSFET switches on and the lamp lights. Switching Circuits (p42 47) The brightness at which Electrical Power (p48 50) – – the lamp turns on can (a) 0V be altered. The light bulb uses up 60 J 15 V of electrical energy every 15 V 13.3 V second. (a) 0V 1900 Ω
As resistance increases, electrons will lose more energy as they pass through the resistor. Therefore, the voltage across the resistor will increase. (a) 125 Ω 225 Ω 1.2 kΩ (a) 250 Ω 300 Ω 40 Ω (a) 3 V 3V 0.5 V (a) 3.8 V 1.0 V 0.6 V (a) V1 = 6 V, V2 = 6 V V1 = 4 V, V2 = 10 V V1 = 7 V, V2 = 3 V V1 = 16 V, V2 = 6 V V1 = 4.5 V, V2 = 13.5 V V1 = 5.5 V, V2 = 3 V Switching Circuits (p42 – 47) (a) 0V 15 V 15 V 0V (a) 4V 8 V 0 V 12 V (a) 700 Ω 3.5 V 2.5 V 3 V 100 °C (a) 6 V 2.5 V 0.016 A (a) (NPN) Transistor As the temperature increases, the resistance of the thermistor decreases. The voltage across the thermistor decreases and the voltage across R1 increases. When this voltage reaches 0.7 V, the transistor switches on and the LED lights. Swap the positions of the thermistor and R1. (a) MOSFET As brightness of light decreases, the resistance of the LDR increases. The voltage across the LDR increases. When this reaches a high enough voltage, the MOSFET switches on and the lamp lights. The brightness at which the lamp turns on can be altered. (a) 13.3 V 1900 Ω 150 Ω This circuit could turn on a fan when a computer overheats. As the temperature increases, the resistance of the thermistor decreases. The voltage across the thermistor decreases and the voltage across R1 increases. When this voltage reaches 0.7 V, the transistor switches on and the LED lights. Electrical Power (p48 – 50) The light bulb uses up 60 J of electrical energy every second.
Electricity-and-Energy-Problem-Booklet-sbu8z8.docx