B - Electricity - Ohms Law of Change Flashcards
What is the formula for current?
Current = charge transfered/time takenor I = Q/tWhere Q – charge measure in coulombs (C) I – current measured in amps (A) t – time measured in seconds (s)
A charge of 60 coulombs is transferred along a conductor in two and a half minutes. Calculate the current.
I = Q/t
I = 60/150 (we have changed the minutes into seconds)
I = 0.4A
If a current of 0.2A flows for an hour, how much charge will be transferred?
I = Q/t
Q = It
Q = 0.2 x 60 x 60 (Note that one hour is 60 minutes of 60 seconds each: 60 x 60 = 3600 s)
Q = 0.2 x 3600
= 720 C
A charge of 200 coulombs is transferred along a conductor in half an hour. Calculate the current.
I = Q/t
I = 200/30 x 60
I = 200/1800
I = 0.111A
If a current of 4A flows for six hours, how much charge will be transferred?
I = Q/t
Q = It
Q = 4 x 6 x 60 x 60
Q = 86400 C
What is Ohms Law?
We can use a formula known as Ohm’s law to relate current voltage and resistance in circuits.
R = V/I
This is usually written as:
V = IR
V – voltage in volts (V)
I – current in amps (A)
R – resistance in ohms (Ω)
Calculate the resistance of a circuit where the voltage is 12V and the current is 0.2A.
R = V/I
R = 12/0.2
R = 60 Ω
An appliance has a resistance of 3000 Ω. Calculate the current that flows through at normal domestic voltage.
R = V/I
I = V/R
I = 230/3000
I = 0.077A
An appliance has a resistance of 200 Ω and a current of 0.5 A. Calculate the voltage of the appliance.
V = IR
V = 0.5 x 200
= 100 V
A bulb has a resistance of 650 Ω and is operated at a voltage of 40 V. Calculate the current in this bulb.
R = V/I
I = V/R
I = 40/650
I = 0.062A
A circuit of resisatnce 26.1 ohms has a voltage across it of 36 volts.
Calculate the current through the circuit.
Give your answer to 3 decimal places.
Include the correct unit in your answer.
1.4A
One volt is defined as being one ________ per _______
joule/coulomb
Current flow in metals is a flow of _____ which have a _______ charge.
Current flow in metals is a flow of electrons which have a negative charge.
current is a flow of ______________
current is a flow of charge
When a LDR is illuminated its resistance _______.
A circuit component designed to change its resistance as its temperature changes is know as a _______.
One component designed to produce light when current passes through it is a _____ emitting _____. This is usually abbreviated to the letters ___________.
When a LDR is illuminated its resistance decreases.
A circuit component designed to change its resistance as its temperature changes is know as a thermistor.
One component designed to produce light when current passes through it is a light emitting diode. This is usually abbreviated to the letters LED.
