Ohms Law and Charge Flashcards
What is the formula for current?
Current = charge transfered/time taken or I = Q/t Where 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.
In a circuit 6262 coulombs of charge are transferred in 7 minutes.
Calculate the size of the current.
Include the correct unit in your answer.
Give the answer to one decimal place.
14.9A
A circuit
A circuit has a resistance of 487 ohms and a current flowing through it of 7.4 amps.
Calculate the voltage across the circuit.
Include the unit in your answer - to one decimal place.
3603.8V
A circuit has a current of 5.0 amps flowing through it when the applied voltage is 21 volts.
Calculate the resistance of the circuit - to one decimal place.
4.2
A current of 5.4 amps flows for 102 seconds.
Calculate the charge transferred in this time.
Include the correct unit in your answer.
Give the answer to one decimal place.
550.8C
How long will it take for a 7.7 amp current to transfer 2477 coulombs of charge?
321.7s