# Calculating Watts in a Day/Second for Lamp with 60W Capacity

• bNo
In summary, the lamp takes 60 watts when connected to a 120-V outlet. It would cost 1468.8 cents to operate the lamp for 24 hrs.
bNo
Hello, I'm having problems with this question. I'm not exactly sure how to determine how much watts in a day, or in a second the lamp takes.

## Homework Statement

Theres a lamp that absorbs 60 W when connected to a 120-V source.
Q: Find the cost of operating the lamp for 24 hrs when electricity cost 6.8cents/kWh.

## Homework Equations

current = power/voltage

## The Attempt at a Solution

1)I took a guess and said 60W equals in one second.
60W(60sec x 60min x 24hrs) = 5,184,000
2)Then, 24hrs into kW = 24000 kW in a day.
3)(5,184,000/24000) x 6.8 cents = 1468.8 cents.

I'm pretty sure I'm missing a formula for time. Thanks for any help.

No, a watt is a unit of power, and a kWh is a unit of energy (power multiplied by time). You are charged for energy by the electric utility company, so they charge you $/kWh. The rest is just being careful with units and cancelling units. bNo said: 60W(60sec x 60min x 24hrs) = 5,184,000 Like in that equation, you were not being careful about units. See if this makes more sense, and keep it going to get to your answer: $$E = Power * Time = 60W * \frac{1kW}{1000W}* 24h * \frac{60 min}{h}$$ berkeman said: No, a watt is a unit of power, and a kWh is a unit of energy (power multiplied by time). You are charged for energy by the electric utility company, so they charge you$/kWh.

The rest is just being careful with units and cancelling units.

Like in that equation, you were not being careful about units. See if this makes more sense, and keep it going to get to your answer:

$$E = Power * Time = 60W * \frac{1kW}{1000W}* 24h * \frac{60 min}{h}$$

EDIT -- Remember to cancel units when you have the same unit over itself, like

$$\frac{W}{W} = 1$$

Thank you for the help. That was the equation I was missing.

Your right I should have put in the units for the result. I need to learn how to do that javascript. It would look a lot nicer than, 60W(60sec/min x 60min/hr x 24hrs)

bNo said:
Thank you for the help. That was the equation I was missing.

Your right I should have put in the units for the result. I need to learn how to do that javascript. It would look a lot nicer than, 60W(60sec/min x 60min/hr x 24hrs)

There's a sticky post at the top of the PF tutorials forum about using LaTex:

https://www.physicsforums.com/forumdisplay.php?f=151

You can also click on the QUOTE button on a post with LaTex in it (like mine above) to see the underlying tex that was used to make the LaTex image. There are also some buttons in the Advanced Reply window that help you to create LaTex equations.

## 1. How do I calculate the number of watts used by a lamp in a day?

To calculate the watts used by a lamp in a day, you will need to know the wattage of the lamp and the number of hours it is used in a day. Multiply the wattage by the number of hours to get the total number of watt-hours used in a day.

## 2. How many watts does a 60W lamp use in a second?

A 60W lamp uses 60 watts in a second. This can also be written as 60 joules per second (J/s) since watts measure the rate of energy consumption.

## 3. Can I convert watts to kilowatt-hours for my lamp?

Yes, you can convert watts to kilowatt-hours for your lamp by dividing the number of watts by 1000. For example, a 60W lamp would use 0.06 kilowatt-hours in an hour.

## 4. How much electricity does a 60W lamp use in a day?

The amount of electricity used by a 60W lamp in a day depends on the number of hours it is used. For example, if the lamp is used for 10 hours in a day, it would use 600 watt-hours or 0.6 kilowatt-hours of electricity.

## 5. Is it more energy-efficient to use a 60W lamp for a longer period of time or a higher wattage lamp for a shorter period of time?

A higher wattage lamp will use more energy in a shorter period of time, while a lower wattage lamp will use less energy over a longer period of time. It is generally more energy-efficient to use a lower wattage lamp for a longer period of time, as it will consume less energy overall.

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