09. P4 Electric Circuits Flashcards
What charge does an electron have?
negative
What does a cell do in a circuit?
Provides energy to the charge flowing through it.
On a cell/battery symbol, which line represents the positive terminal?
longer line
What does a resistor do in the circuit?
It resists the flow of the current through it, energy is transferred into heat energy
What is the energy change taking place in a battery/cell?
Chemical into electrical and heat
What is the direction of conventional current?
Travels from positive to negative terminal
What direction does the electrons flow in a circuit when connected?
Electrons flow from negative terminal to the positive terminal
What does a bulb do in the circuit?
Converts electrical energy into light and heat energy
What does a diode do?
It only allows current to flow in one direction
What device is used to measure the current in a circuit?
Ammeter
What is an LDR?
Light Dependent Resistor = device whose resistance decreases as more light shines on it
What is a thermistor?
Device whose resistance decreases as temperature increases
What device can be added to a circuit to allow the used to alter the current flowing in a circuit?
Variable Resistor
What is the purpose of a voltmeter?
It is used to measure the potential difference across a device
How can thermistors be used in a device?
Temperature sensor
How can a LDR be used in a device?
Light level sensor
What happens to the resistance of a thermistor when the temperature increases?
Resistance decreases
What happens to the resistance of a LDR when the light level increases?
Resistance decreases
Rule for current measurement in a series circuit?
Current is the same at any point in the circuit
Rule for current measurement in a parallel circuit?
Current leaving the battery splits between each of the branches in the circuit (Battery current = A1 + A2+ A3…)
What is electric charge measured in?
Coulombs
What is the symbol used for electric current?
Q
What is the symbol used for coulombs?
C
What are the units of resistance?
Ohms
State what is meant by resistors obeying Ohm’s law?
At a constant temperature, the current through a resistor is directly proportional to the voltage across it
Name a component which is said to be an ohmic conductor?
Resistor
In an I-V graph, a steep line(high gradient) indicates what about the component being tested?
High gradient = low resistance
Explain the curved feature of the IV plot of a filament lamp?
As the PD increases, the current increases,causing the temperature to increases so the resistance increases.
Why is the diodes IV plot a flat horizontal line along the X-axis in the reverse direction?
Because the resistance is very high in reverse direction, as it only allows current to flow in one direction.
At what PD across a diode in the forward direction, does the current start to flow?
0.6V
What happens to the PD of the battery in a series circuit?
The PD is shared across each of the components
What determines the share of the PD across components in a series circuit?
The resistance, a component with a higher resistance compared to the others will have a bigger share.
What is the total resistance in a series circuit equal to?
For a series circuit, the total resistance is equal to the sum of all the components resistors in the circuit
What happens to the PD of the battery in a parallel circuit?
The PD over the battery is the same as the PD over each of the branches in the parallel circuit.
What happens to the total resistance when you add more resistors in parallel?
The total resistance decreases
What are the requirements for a static charge to buildup on an object? PHYSICS ONLY
Friction between two insulators, electrons transfer from one object to another.
Explain in terms of electrons why a polythene rod becomes negatively charged when rubbed with a dry cloth… PHYSICS ONLY
Electrons transfer from the surface atoms of the cloth to the rod so the rod becomes negatively charged
