Video Transcript
The diagram shows a circuit
consisting of a battery, a resistor, and a voltmeter. The resistor has a resistance of 30
ohms, and the reading on the voltmeter is six volts. What is the current through the
resistor?
In this question, we see a diagram
of an electric circuit that has a battery providing a potential difference. We see that there is a resistor
connected in series with the battery, so the battery produces a potential difference
across the resistor. The potential difference across the
resistor produces a current in the resistor. There is actually a current in the
entire circuit, which is equal to the current in the resistor. We also see that a voltmeter is
connected in parallel with the resistor. The voltmeter is correctly
connected to measure the potential difference across the resistor, and it reads six
V, which stands for six volts.
The question states that the
resistance of the resistor is 30 Ω, which stands for 30 ohms. Ohm’s law states that, for two
points in a circuit, the potential difference across the points equals the current
between the points multiplied by the resistance of the object between the
points. Written as an equation, 𝑉 stands
for the potential difference across the resistor, 𝐼 stands for the current in the
resistor, and 𝑅 stands for the resistance of the resistor. To find the current, we must make
𝐼 the subject of the equation. We can do this by dividing both
sides of the equation by resistance. This gives us the equation current
is equal to the potential difference divided by the resistance.
Let’s take a look at the units in
this equation before we begin putting in the given values and finding the
current. On the right-hand side, we have the
unit of volts divided by the unit ohms. On the left-hand side, we have the
unit of amperes, the unit of electric current. Now that we have this equation and
know the units for it, let’s substitute into the equation the values given in the
question. The current through the resistor is
equal to six volts divided by 30 ohms. This gives us a value of 0.2
amperes. This is the current through the
resistor.
