Describe one technique you could use to measure the threshold voltage for LEDs.
A sensitive ammeter is placed in series with LED. With the increase in Voltage, measure the potential difference value when it starts conducting. Black-out and shaded vision tube is used to observe the voltage value when visible light is first observed as the voltage is increased.
MP
Related Physics A Level answers
All answers ▸A ball is hit horizontally at a height of 1.2 m and travels a horizontal distance of 5.0 m before reaching the ground. The ball is at rest when hit. Calculate the initial horizontal velocity given to the ball when it was hit.
If you have 1.33g of oxygen (Mr = 32) in a container of volume 1000cm^3 at atmospheric pressure (101.3*10^3 Pa), what is the temperature of the gas in Celsius? R=8.314
An ideal gas at a temperature of 22 C is trapped in a metal cylinder of volume 0.2 m^3 at a pressure of 1.6x10^6 Pa. The gas has a molar mass of 4.3 x 10^(-2) kg mol^(-1). Calculate the density of the gas in the cylinder.
What does the photoelectric effect demonstrate?