Electricity Flashcards
When certain insulating materials are rubbed against one another what happens to them?
One becomes negatively charged.
Why do materials become negatively charged when rubbing against one another?
They rub off negatively charged electrons onto the other.
The material that gains electrons when rubbing against another insulating material becomes what?
Negatively charged.
The material that loses electrons when rubbing against another insulating material becomes what?
Positively charged (equal to that of the material gaining electrons).
When two electrically charged objects are brought together they do what to each other?
Exert a force on each other.
Two objects that carry the same type of charge…
…repel.
Two objects that carry different types of charges…
…attract.
Electrical charges can what through metals?
Move more easily.
Electrical current is what?
The flow of electrical charge. Size of current indicates the rate of flow.
Equation for current:
I = Q/t
Where:
I is current (A)
Q is charge (C)
t is time (s)
What is potential difference (voltage) between two points in a circuit?
The work done (energy transferred) per coulomb (C) of charge that passes between the points.
Equation for potential difference (voltage):
V = W/Q
Where:
V is potential difference (V)
W is work done (J)
Q is charge (C)
Circuit diagram symbols:
Two horizontal lines with a gap where one line is at 45 degrees. Open Switch.
Two horizontal lines with a join in the centre. Closed Switch.
A circle with an ‘x’ inside, attached to a horizontal line either side. Lamp.
Two ‘t’ shapes head to head, one with a thicker top. Cell
Three t-shapes, the one on left flipped to the right, the two on the right flipped 90 degrees to the left. the two on the right side have a thicker “top”. Battery.
A circle with a ‘V’ in the centre. two horizontal lines come out from either side of the circle. Voltmeter.
A rectangle lying flat with two horizontal lines coming out of its sides. Resistor.
A rectangle lying flat with one horizontal line running through the centre of it and out of both sides. Fuse.
A circle with an ‘A’ in the centre with two horizontal lines coming out of the sides of the circle. Ammeter.
A rectangle lying flat with an arrow running through it at a 45 degree angle. Two horizontal lines run out of the sides of the rectangle. Variable resistor.
A rectangle lying flat with two horizontal lines running out either side of it. A 45 degree line runs through the rectangle which bends at the bottom to run parallel with the base of the rectangle. Thermistor.
A rectangle lying flat with two horizontal lines running out of either side. A circle runs around the rectangle, and two arrows point downwards at the rectangle, from the top left. Light dependent resistor (LDR)
Circuit symbol for LED. Light emitting diode (LED).
Circuit symbol for diode. Diode.
Current-potential difference (voltage) graphs are used to show what?
How the current of a component varies as the potential difference varies across it.
Describe the current-potential difference graph for a resistor at a constant temperature.
A straight line that is directly proportional (positively correlating).
Resistance of a component can be found how?
By measuring the current through it and the potential difference across it.
The current through a resistor can be described as what to the potential difference across it?
Directly proportional.
Resistance equation:
V = IR
Where:
V is potential difference in volts.
I is current in amps.
R is resistance in ohms.
Current through a component depends upon what?
The component’s resistance.
The greater the resistance of a component…
…the smaller the current for a given potential difference across a component.
The potential difference provided by cells connected in series is…
…the sum of the potential difference of each cell (depending upon which way they are connected).
For components connected in series:
The total resistance is the sum of the resistance for each component.
There is the same current throughout each component.
The potential difference of the supply is shared between the components.
For components connected in parallel:
The potential difference across each component is the same.
The current through the whole circuit is the sum of the currents through the separate components.
True or false, the resistance of a filament bulb increases as temperature decreases.
False, resistance of a filament bulb increases as temperature increases.
Describe the shape of a current-potential difference graph for a filament bulb.
S-shaped through the origin.
Why does resistance increase in a filament bulb as current increases?
As current increases the filament increases in temperature because electrons collide with the ions in the metal making it more difficult for electrons to travel at a speed directly proportional to potential difference.
Current through a diode flows…
…in one direction only.
A diode has a high resistance when?
When the current is flowing in reverse.
Describe a current-potential difference graph of a diode.
Flat line on x-axis in quadrant 2, then past y-axis into quadrant 1 current increases as potential difference increases.
LEDs emit light when what?
Current is flowing in a flowing in a forward direction.
Resistance of a light dependent resistor decreases as…
…light intensity increases.
Resistance of a thermistor decreases as…
…temperature increases.
