# Current through the circuit with resistor and light bulb

• ashyau
In summary, the conversation discusses a problem given in an image, involving a series circuit and the equation V=IR. The person attempted to solve the problem by considering the current to be the same and calculated it to be 9/20, but the answer given is 0.3Ω. The conversation then delves into the resistance of the lamp, which is not actually zero but variable according to a curved dashed line. The suggested approach to solving the problem is through an iterative graphical method.
ashyau

## Homework Statement

Problem is give in the image

V=IR

## The Attempt at a Solution

Since its a series circuit i tried that current should be the same so it's 9/20 since there is no resistance in the bulb which is 0.45 Ω somehow the answer is 0.3Ω. why is that the case? should be something to do with the graph but i have no idea what to do with it

#### Attachments

• ss.JPG
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In the image you've provided, it's difficult to tell what's being asked. I assume that you're supposed to finish the sentence: The current in the circuit is ______. Is that correct?

Last edited:
The resistance in the lamp is not zero. It is variable--described by the curved dashed line. The answer has units of "A", not "Ω". Try an iterative graphical approach--pick some starting value for the lamp resistance, say 20Ω, find the resulting current then use that current to determine a better value for lamp resistance. Repeat process until your lamp resistance converges.

## 1. What is the purpose of a resistor in a circuit?

A resistor is used to limit the flow of electric current in a circuit. It reduces the amount of current that passes through the circuit and helps to protect other components from damage.

## 2. How does the amount of current change when a resistor is added to a circuit?

Adding a resistor to a circuit will decrease the amount of current that flows through the circuit. The resistor creates resistance, which reduces the flow of current.

## 3. What happens to the resistor when the current through the circuit increases?

As the current through the circuit increases, the resistor may start to heat up due to the increased flow of electrons. This can cause the resistor to dissipate more energy and potentially become damaged.

## 4. What is the relationship between current, resistance, and voltage in a circuit?

According to Ohm's law, the relationship between current, resistance, and voltage is given by the equation V=IR, where V is the voltage, I is the current, and R is the resistance. This means that as the resistance increases, the current decreases, and vice versa.

## 5. How does a light bulb affect the current in a circuit?

The light bulb acts as a resistor in a circuit, which means it limits the flow of current. As the current passes through the filament of the light bulb, it heats up and produces light. This causes a decrease in the overall current in the circuit.

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