# Power consumption for a specific time period

• mathew086
In summary: If so, how much power is consumed continuously for 1 hour?In summary, the circuit consumes 49.5mW continuously for 1 hour.
mathew086

## Homework Statement

Given circuit consists of two resistors ( R1 = 330 Ohm , R2 = 22K Ohm ) , an LED ( Forward voltage = 1.6V, forward current = 20 mA) , a BC 337 NPN transistor and a 9V battery supply. I need to find the total power consumed by the circuit for a run time of continuous 1 hour?

V = IR
P = VI

## The Attempt at a Solution

taking the right side of the circuit and appyling the V = IR
9 = (I *330) +(1.6)+voltage across the NPN transistor

I am not sure about the voltage across the NPN transistor.

And on the left side applying V= IR
9= I *22000
giving I = 4.09*10^-4=400 uA.

Is total power consumed by the circuit = sum of power consumed by all individual elements??

#### Attachments

• Circuit_.jpg
9.4 KB · Views: 380
It's easier to calculat the total current of the circuit, which is the sum of the currents through the 2 resistances, or the Base-emitter current and the Collector-emittor current.
The power is (current drawn) * (supply voltage)

This is a common emitter ampiflier, without an emitter resistance. Compute the base-emitter current first. You have the 22k resistance in series with the base-emitter voltage (look up on dataheet). Now the collector - emittor current is the current gain (at least 100 for this transistor) * the base-emittor current.
The current gain can't be larger than the current you get if the transistor is saturated. This maximum current is what you get if you put the 330ohm resistance, the led and the saturation voltage of the transistor in series.

Is it a common base transistor or common emitter, ?
http://www.datasheetcatalog.org/datasheet2/3/06i96k727i3oloo2gis1ozg0jlyy.pdf"

In the data sheet the Base-emitter current is given as 1.2V ( max) [under the given conditons Ic = 500 mA, Vce = 1V]
So Emitter base current = 1.2/22 *1000 =0.0545 mA
Collector meitter current = 100 *0.0545 = 5.45mA

So total current = 5.5045mA
Therfore P = 5.5045 *9/1000 = 49.5mW..

This is power consumed for how much time? If the circuit runs for 5 mins continously then power = ?

Is that so?

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## What is "power consumption for a specific time period"?

"Power consumption for a specific time period" refers to the amount of energy that is used by a device or system during a specific period of time. This can be measured in units such as kilowatt-hours (kWh) or joules (J).

## Why is it important to track power consumption for a specific time period?

Tracking power consumption allows us to understand the energy usage patterns of a device or system over a specific time period. This information can help identify opportunities for energy efficiency improvements and reduce overall energy costs.

## How is power consumption for a specific time period measured?

Power consumption is typically measured using a device called an energy meter, which tracks the amount of energy used over a specific time period. This data can also be collected and analyzed using energy monitoring software.

## What factors can impact power consumption for a specific time period?

Power consumption can be affected by a variety of factors, including the type and efficiency of the device, the length of time it is in use, and external factors such as temperature and humidity. Additionally, user behavior and settings can also impact power consumption.

## How can power consumption be reduced for a specific time period?

There are several ways to reduce power consumption for a specific time period, including using energy-efficient devices, adjusting settings to optimize energy usage, and implementing energy-saving practices such as turning off devices when not in use. Regular monitoring and analysis of energy usage data can also help identify opportunities for improvement.

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