Question Video: Understanding the Relation between Current, Charge and Time | Nagwa Question Video: Understanding the Relation between Current, Charge and Time | Nagwa

# Question Video: Understanding the Relation between Current, Charge and Time Science • Third Year of Preparatory School

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David sets up three circuits. He measures how much charge flows through each circuit in the same amount of time. His results are shown in the following table. Which circuit has the greatest current?

02:22

### Video Transcript

David sets up three circuits. He measures how much charge flows through each circuit in the same amount of time. His results are shown in the following table. Which circuit has the greatest current?

We need to determine which of circuits one, two, and three has the greatest current based on the information in this table. To practice calculating the current in a circuit, we will calculate the current in each circuit from the charge and time in the table and then compare those results. Recall that we can calculate current from the equation 𝐼 equals 𝑄 divided by 𝑡, where 𝐼 is the current measured in amperes, 𝑄 is the charge measured in coulombs, and 𝑡 is the time measured in seconds. All we need to do now is substitute the values from each circuit into this equation.

In circuit number one, the charge is 20 coulombs and the time is five seconds. So using 𝐼 equals 𝑄 divided by 𝑡, we have 20 divided by five, which is four. And since our units for charge are coulombs and our units for time are seconds, the units for this current are coulombs per second, or amperes. So the current in circuit one is four amperes. In circuit number two, the charge is 25 coulombs and the time is five seconds. Since the units for charge and time are again coulombs and seconds, the current will again have units of amperes, and its numerical value will be 25 divided by five. 25 divided by five is just five. So the current in the second circuit is five amperes.

Finally, in the third circuit, the charge is 12 coulombs and the time is again five seconds. The units for charge and time are again coulombs and seconds, so the units for the current will again be amperes. And the numerical value will this time be 12 divided by five. Since 12 divided by five is 2.4, the current in the third circuit is 2.4 amperes. Now that we have calculated the current in each circuit, we can see immediately that the greatest current is five amperes in circuit two. So the circuit with the greatest current is circuit two.

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