Question

# A TV set shoots out a beam of electrons. The beam current is 10 A. How many electrons strike the TV screen in a minute?

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Solution

## Step 1: Concept usedCharge is defined as the property of material because of which it can experience magnetic or electric force when kept in electromagnetic field.The mathematical expression of charge is $\mathrm{q}=\mathrm{It}$, where $\mathrm{q}$ = charge, $\mathrm{I}$ = current and $\mathrm{t}$ = time.The net charge of a body can be expressed as the integral multiples of the basic unit of charge.The mathematical expression to express net charge as an integral multiple of the basic unit charge is given as: $\mathrm{q}=\mathrm{ne}$, Where, $\mathrm{q}$ is the charge, $\mathrm{n}$ is the number of electron, $\mathrm{e}$ is the charge on the electron ( basic unit charge) which is equal to $1.6×{10}^{-19}\mathrm{C}$.Step 2: Given parametersCurrent, $\text{I=}10\mathrm{A}$ Step 3: CalculationSo the charge in the beam of electron for one minute is given by,$\mathrm{q}=\mathrm{It}$Where, $\mathrm{q}$ is the charge, $\text{I}$ is the current, and, $\text{t}$ is the time for which the current is flowing.Substitute the values,$\mathrm{q}=10\mathrm{A}×60\mathrm{s}$$\mathrm{q}=600\mathrm{C}$As we know that we can express charge as the integral multiple of basic charge, we can write charge as,$\mathrm{q}=\mathrm{ne}$$\mathrm{q}=\mathrm{n}\left(1.6×{10}^{-19}\mathrm{C}\right)$Putting both the values of charge equal to each other :$\mathrm{n}\left(1.6×{10}^{-19}\mathrm{C}\right)=600\mathrm{C}$$\mathrm{n}=\frac{600\mathrm{C}}{1.6×{10}^{-19}\mathrm{C}}$$\mathrm{n}=375×{10}^{19}$.Thus the total electrons strike the TV screen in a minute are $375×{10}^{19}$.

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