Coulombs and ampere are both normally used when studying electricity, and it is crucial to remember that they measure different things. The coulomb measures charge, and the ampere measures the *flow* of charge. One ampere of current is equal to one coulomb of charge passing a sharpen in a wire in one second. We can measure how much charge passes over any distance of time—it does not need to be only one second. We plainly find current by dividing an sum of charge by how much fourth dimension the tear was measured for. current can be calculated using the recipe 𝐼=𝑄𝑡, where 𝐼 represents the stream, 𝑄 represents charge, and 𝑡 represents fourth dimension .

### Definition: Electric Current in a Wire

The electric current, 𝐼, in a cable can be found using the formula 𝐼=𝑄𝑡, where 𝑄 represents an amount of charge that passes a point in the wire over some sum of meter, 𝑡. We can practice using this equation by working through some examples .

### Example 1: Calculating Charge Flow given Current

The diagram shows an electric tour containing a cell and a medulla oblongata. The current in the lap is 2 amperes. How much charge flows past point P in the circuit in 1 second ?

### Answer

recall that one ampere of current is defined as one coulomb of charge pass by a orient in one second. We are told that the current in the lap is 2 A. consequently, we know that 2 coulombs of charge passes point P in 1 second .

### Example 2: Comparing Currents in Multiple Circuits

Fares sets up three circuits. He measures how much charge flows through each circuit in the like total of time. His results are shown in the follow postpone .

Charge | Time | |
---|---|---|

Circuit 1 | 20 coulombs | 5 seconds |

Circuit 2 | 25 coulombs | 5 seconds |

Circuit 3 | 12 coulombs | 5 seconds |

Which circumference has the greatest stream ?

### Answer

Recall that stream can be found using the convention 𝐼=𝑄𝑡, where 𝐼 is the current, 𝑄 represents charge, and 𝑡 represents time. We will substitute values from the mesa into the equality above to calculate stream values 𝐼, 𝐼, and 𝐼. The subscripts 1, 2, and 3 tell which circuit the current is measured for. Substituting in the charge and clock time measurements form circuit 1, we have 𝐼=205=4.CsA therefore, the current in circumference 1 is 4 amperes. Moving on to circuit 2, we have 𝐼=255=5.CsA The current in circuit 2 is 5 amperes. For lap 3, 𝐼=125=2.4.CsA So the stream in lap 3 is 2.4 amperes. consequently, **circuit 2** has the greatest current .

### Example 3: Comparing Currents in Multiple Circuits

The diagram shows two circuits, racing circuit 1 and circuit 2. In circumference 1, 28 coulomb of mission flows through the medulla oblongata in 14 seconds. In tour 2, 9 coulomb of charge flows through the buzzer in 3 seconds. In which racing circuit is the stream greater ?

### Answer

We want to compare the current in two unlike circuits. Recall the formula for calculating current, 𝐼=𝑄𝑡, where 𝐼 is current, 𝑄 represents charge, and 𝑡 represents time. We can find the current in the circuits by substituting the given amounts of charge and time for each circuit into this equality. For lap 1, we have 𝐼=2814=2.CsA so, we have found that the current in circuit 1 is 2 amperes.

For circumference 2, we have 𝐼=93=3.CsA The current in circuit 2 is 3 amperes. therefore, the stream is greater in **circuit 2** .

### Example 4: The Relation between the Current and the Amount of Charge Moving in a Circuit

The diagram shows an electric racing circuit containing a cell and a bulb. The total of charge flowing past period P in one moment is 12 coulomb. If the sum of charge flowing past sharpen P in one second were to double, by what factor would the current in the lap change ?

### Answer

We want to understand how doubling the amount of charge flowing past a degree affects the current in a lap. We can start by remembering the formula for current, 𝐼=𝑄𝑡, where 𝐼 is current, 𝑄 represents commission, and 𝑡 represents time. We will use this formula to find two current values, which we will call 𝐼o and 𝐼d. The subscripts o and d specify the circuit with the *original* or *doubled* amount of charge. To calculate the original total of current, we have 𝐼=121=12, oCsA so the stream is in the first place 12 amperes. After the come of commit doubles, there is 24 coulomb passing point P in one second. Substituting this into the equation, we have 𝐼=241=24.dCsA After the charge is doubled, the stream is 24 amperes. therefore, increasing the accusation passing point P in one moment by a factor of 2 causes the current to **increase by a
factor of 2** .

### Example 5: Understanding Electric Current in a Circuit

Describe what is meant by the phrase *the electric current in a circuit* .

### Answer

We have been asked to write a curtly description of electric current in a racing circuit. To begin, recall that electric current is the movement of electric charge. stream measures how quickly charge moves through something. In a circuit, we see negatively charged electrons moving through a wire. We look at one point in the wire to measure its current . Let us finish by summarizing some significant concepts .

### Key Points

- Electric charge is measured in units of
coulombs

;the symbol for the

coulomb isC

.

- Electric current is measured in units of
amperes

;the symbol for the

ampere isA

.

- One ampere

is equal to one coulomb

passing a point in a wire in onesecond

.

- We can calculate current, 𝐼,
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using the formula 𝐼=𝑄𝑡 ,where 𝑄 represents an amount of charge passing a point in an amount of time, 𝑡 .