Buscar
Estás en modo de exploración. debe iniciar sesión para usar MEMORY

   Inicia sesión para empezar

level: Level 1 of Chapter 11

Questions and Answers List

level questions: Level 1 of Chapter 11

QuestionAnswer
You cannot assume that it is providing you with exact voltage across its terminals as suggested by the value of e.m.f. Give 3 examples why?1. Supply may not be made to high degree of precision 2. Batteries may have become flat 3. All sources of e.m.f have an internal resistance
The charges moving round a circuit have to pass through what 2 things1. External components 2. Internal resistance of power supply
Power supplies and batteries get warm when they are in use, why?Some of the electrical potential energy of the charge is transformed to internal energy as they do work against the internal resistance of the cell
Potential difference across the internal resistance indicates what?Indicates energy transferred to the internal resistance of the supply
What is the formula used to calculate Potential difference across a power source:V = E - Ir
What does the terminal p.d. of the battery depend on?the resistance of an external resistor
What arrangement of resistors do we use when you only want to use part of the e.m.f. of a supplyPotential divider circuit
What is the potential divider equationV'out' = (R₂ ➗(R₁ + R₂)) ✖️ V 'in'
How is a light-dependent resistor (LDR) used as a sensor or transducerVoltage is needed to drive the output devices, such as a voltmeter, yet the LDR only produces a change in resistance Sensor must use this change in resistance to generate the change in voltage Solution is to place the LDR in series with a fixed resistors
Negative temperature coefficient means that,when temperature rises, resistance of the theristor falls
In a negative temperature coefficient, when the temperature rises, resistance of the theristor falls why?Thermistor is made from a semiconductor material, so when temperature rises the number of free electrons increases, thus resistance falls
What is a potentiometerdevice used for comparing potential differences
What can a potentiometer be used formeasure e.m.f. of a cell, provided you already have a source whose e.m.f. is known accurately
A potentiometer consists of whata piece of resistance wire, usually 1m in length, stretched horizontally between 2 points
What is a jokeySimple connecting device with a very sharp edge that allows very precise positioning on the wire
What is a null methodfinding a point where the reading is zero