Resistance and Increase in Current

In summary, resistors are used in circuits to limit the current. They lose energy, slowing down the movement of electrons. Adding more batteries in a series circuit increases the current, but the overall resistance remains the same. The formula for current is I = V/R (current = voltage divided by resistance). The human body acts as a resistance, and the amount of current depends on the potential difference. A parachutist holding onto one power line cable will not experience a shock because there is no complete circuit. However, if they were holding onto two cables with a significant potential difference, they would get electrocuted. The resistance between the hands on one cable is too small to cause any noticeable potential difference.
  • #1
Peter G.
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I was reading about resistance and it said that resistors are used to limit the current in a circuit. How does a resistor reduce the current in a series circuit? They lose energy therefore they move slower? Or does it simply prevent electron flow?

In addition to that, how does adding more batteries in a series circuit increase the current? Well, I mean: In the example there is a series circuit with an ammeter, and a resistor with a voltmeter connected to measure the potential difference across the resistor or across the battery I can't remember, but there was just one resistor anyway. The resistor was the same: Whenever batteries were added, the potential difference increased and the current increased. I am guessing the current was still the "same" but with more energy (voltage) a greater current was able to be pushed through the resistor.
 
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  • #2
Yes, the greater the potential the more current that goes through the resistance. The formula is I = V/R (current = voltage divided by resistance). The human body is similar to a resistance. If you touch your hands to a 12 Volt car battery, so little current goes through you that you don't even feel a shock. A 120 Volt source is quite different.
 
  • #3
Ah ok, got it.

I am just having a bit of trouble with a more specific problem. Towards the end of the resistance video they portray a parachutist holding on with both his hands to a power line cable. It says that the parachutist does not experience a shock because the potential difference between both his hands is very small, not allowing current to run through his body. However, the charge, I believe, has quite a lot of energy, due to its high voltage, enabling a big potential difference if it goes through a resistor. So wouldn't that charge running through him, a resistance, allow a lot of current to run through him? I am thinking he does not get electrocuted because the electricity is being transported at very low current to avoid energy lost by heat so, no matter the potential difference, the current from a start is already pretty low.

Do you think you can help me clear this out?
 
  • #4
The guy must be holding onto just one cable. If he had his hands on two cables with a few KV potential difference between them, he would indeed get roasted. But touching one, no current flows because their is no complete circuit.

Holding two hands on one wire with half a meter between them, there would be a tiny potential difference between hands. Power lines typically have a resistance of a few ohms per km, but the resistance between hands and the resulting V = I*R potential difference from one hand to the other would be too small to notice.
 
  • #5


I can provide a more detailed explanation of how a resistor reduces the current in a series circuit. A resistor is a component that is designed to have a specific amount of resistance to the flow of electric current. This resistance is measured in ohms, and it is determined by the material, size, and shape of the resistor.

In a series circuit, the resistors are connected in a single path, so the current must pass through each resistor in order. This means that the total resistance in the circuit is equal to the sum of the individual resistances. Therefore, when a resistor is added to a circuit, it increases the total resistance and limits the flow of current.

One way to think about this is through the analogy of a water pipe. Imagine that the current is like water flowing through a pipe, and the resistor is like a narrow section of the pipe. When the water reaches the narrow section, it has to slow down and squeeze through, which limits the overall flow of water. Similarly, when the current reaches a resistor, it has to slow down and navigate through the resistance, which reduces the overall flow of current.

Now, onto the second part of your question about adding more batteries in a series circuit. In a series circuit, the voltage (or potential difference) is divided between the different components. This means that adding more batteries in series will increase the total voltage in the circuit. This increase in voltage will also increase the current, as you observed.

To understand why this happens, we need to look at Ohm's Law, which states that the current in a circuit is directly proportional to the voltage and inversely proportional to the resistance. This means that when the voltage increases, the current will also increase, as long as the resistance remains constant.

In your example, the current was still the same because the resistance of the circuit remained constant. However, with the increase in voltage from the additional batteries, the current was able to increase as well.

In summary, resistors limit the flow of current in a series circuit by adding resistance, while adding more batteries in series increases the voltage and therefore increases the current, as long as the resistance remains constant. I hope this explanation helps to clarify the relationship between resistance and current in a series circuit.
 

1. What is resistance?

Resistance is the measure of how much a material or device impedes the flow of electric current. It is measured in ohms (Ω) and is determined by the material's properties, such as its length, cross-sectional area, and temperature.

2. How does resistance affect current?

In general, the higher the resistance, the lower the current. This is because resistance restricts the flow of electrons, making it more difficult for current to pass through a circuit. However, in some cases, an increase in resistance can lead to an increase in current if the voltage is also increased.

3. What factors can cause an increase in resistance?

There are several factors that can cause an increase in resistance, such as the length of a wire, the material it is made of, and the temperature. Additionally, any damage or corrosion to the wire can also increase resistance.

4. How does increasing current affect resistance?

Increasing current can also increase resistance in some cases. This is because as the current increases, the temperature of the material may also increase, causing an increase in resistance. Additionally, as more current flows through a wire, it can cause the wire to heat up and expand, which can also increase resistance.

5. How do you calculate resistance and current?

The relationship between resistance, current, and voltage is described by Ohm's Law: R = V/I, where R is resistance in ohms, V is voltage in volts, and I is current in amps. This means that to calculate resistance, you would divide the voltage by the current, and to calculate current, you would divide the voltage by the resistance.

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