P2.3 Currents in electrical circuits Flashcards
(53 cards)
What happens when 2 electrically charged objects are brought together?
they exert a force on each other
When will 2 objects attract?
if the 2 objects carry different types of charge (have opposite electric charge +, -)
When will 2 objects repel?
When the 2 objects carry the same type of charge ( +,+ or -, -)
What materials can electrical charges move easily through?
good conductors- eg metals
What is electric current?
a flow of electric charge
What is the size of electric current?
the rate of flow of electric charge
in the equation
I = Q (divided by) t
what do the letters stand for and what are the units?
I- current in amps (A)
Q- charge in coulombs (C)
t-time (s)
When does more charge pass around a circuit?
when a bigger current flows
What is potential difference (voltage) ?
the energy transferred per coulomb of charge that passes between 2 points in a circuit
What is resistance?
Anything in the circuit which slows the current down
The greater the resistance across a component…….
the smaller the current that flows
What is the potential difference between 2 points in an electrical circuit?
the work done (energy transferred) per coulomb of charge that passes between the points
(amount of energy that is transferred per unit of charge)
In the equation
V = W (divided by) Q
what does each letter stand for and what are the units?
V- potential difference (V)
W- work done (J)
Q- charge in coulombs (C)
What is another word for voltage?
potential difference (p.d)
Describe a thermistor and its uses
- is a temperature dependent resistor
- in hot conditions the resistance drops, so more current
- in cool conditions the resistance goes up, so less current
- make useful temperature detectors eg- thermostats + car engine temperature sensors
Describe light dependent resistors (LDR) and its uses
- dependent on INTENSITY of light
- bright light, resistance falls- more current
- darkness, resistance increases- less current
- useful as automatic night lights, out door lighting and burglar detectors
What are current-potential difference graphs used to show?
how the current through a component varies with the potential difference across it
What happens when certain insulating materials are rubbed against each other?
They become electrically charged
because negatively charged electrons are rubbed off one material and on to the other
The material that gains electrons becomes negatively charged and the material that loses electrons is left with an equal positive charge
The electrically charged materials attract smaller objects near them
Describe the current-potential difference graph for a resistor
(eg LDR or thermistor)
The current through a resistor is directly proportional to the P.D
Describe the current-potential difference graph for a resistor
(eg LDR or thermistor)
The current through a resistor is directly proportional to the P.D
Why in an LDR the more light, the more current?
as with more light there is less resistance
this is because light allows electrons to have energy and flow
Why in a thermistor the higher the temperature, the greater the current?
as the higher the temperature, the less resistance
This is because the temperature causes the electrons to have more energy and move due to increased kinetic energy of particles
Describe the current-potential difference graph for a filament lamp
a curve
as the temperature of the filament increases and resistance increases
In a filament bulb, why does increasing the temperature increase the resistance?
with a higher temperature, the ions in the conductor vibrate more which makes it harder for the electrons to get through the resistor, meaning the resistance increases
