P2 - Electricity Flashcards
What is the charge of electrons? How does this affect movement in a circuit?
. Negative
. Electrons are repelled by the negative end of the cell
What is current?
The flow of electrical charge.
What is current measured in? using which equipment?
Amps
Ammeter
What is the equation for current?
Charge flow (C) = current (A) x time (s)
Rearranged:
Current = charge flow ÷ time
What is potential difference?
The energy transferred, per coulomb of charge that passes, between two points in a circuit.
What is potential difference measured in? using which equipment?
Volts
Voltmeter
What is the equation for potential difference?
potential difference (v) = current (A) x resistance (Ω)
V = i x R
What is resistance?
When conductors oppose the flow of electrical current.
What is the equation for resistance?
Resistance = potential difference ÷ current
What is the equation for charge flow?
Charge flow (c) = current (A) x time (s)
Q = it
What is the equation for energy transferred?
Energy transferred (j) = charge flow (c) x potential difference (v)
Energy transferred = power x time
What does I-V characteristic mean?
A graph which shows how the current (i) flowing through a component changes as the potential difference (v) across it is increased.
Linear components have an I-V characteristic that is a straight line
Non-linear components have an I-V characteristic that is a curved line
What is the shape of an I-V characteristic graph for an ohmic conductor?
A straight line because current through an ohmic conductor (at a constant temperature) is directly proportional to potential difference.
What is the shape of an I-V characteristic graph for a filament lamp?
A curved line because…
As current increases, the temperature of the filament increases, so the resistance increases. This means less current can flow per unit pd, so the graph gets shallower.
What is the shape of an I-V characteristic graph for a diode?
What is a thermistor?
A thermistor is a temperature dependent resistor.
In hot conditions, the resistance drops.
In cold conditions, the resistance goes up.
Thermistors make useful temperature detectors, e.g. car engine temperature sensors and electronic thermostats.
What is an LDR?
What is it used for?
A light dependent resistor
= A resistor that is dependent on the intensity of light
In bright light, the resistance is lower
In darkness, the resistance is higher
Used for automatic night lights, outdoor lighting, and burglar detectors.
How are sensing circuits used?
???? How are LDRs and thermistors used in sensing circuits?
Sensing circuits can be used to turn on or increase the power to components depending on the conditions that they are in.
What is a series circuit?
What is a parallel circuit?
Investigate resistance in a series circuit
Investigate resistance in a parallel circuit
Your results should match the resistance rules
Why is the voltmeter placed in parallel to the component?
Because the voltmeter measures the difference in the energy the electrons have before they go into the component and after they have left it.
