Do you know how to read an analog energy meter and pointers? A question came up at ENEM in which it was necessary to know how to read an electricity meter, where some students did not know how to ask the question. So in this article, we will show you how to read the light clock and calculate the consumption of a house. Come on!

# What is the energy meter?

The electricity meter is popularly known as the light clock. They have the function of measuring the electricity consumption of a given installation. Energy meters measure electricity consumption monthly in kWh. KWh means Kilowatt-hours and the measure of the electrical energy consumed by an appliance in a given period. Therefore, one Watt-hour represents the amount of energy needed to power equipment that has a power of 1 Watt for one hour.

The energy meters perform the direct measurement of the electric current, the direct measurement of the energy consumed by the load passes entirely through the measuring equipment. There are two different ways to perform an electrical current measurement, which is direct measurement and indirect measurement .p

The first-kilowatt-hour meter of alternating current by induction was presented to the public by the Hungarian Ottó Bláthy in 1889. Ottó Bláthy showed the energy meter at the Frankfurt Fair and the success was so great that in the same year it was already being marketed.

# Energy Meter Reading – Issue of ENEM

The ESMS is very busy throughout Brazil and requires expertise in various disciplines and general knowledge, a good example was an issue that had to know how to read a power meter, the question fell in the proof of ENEM was this:

Electricity consumed in homes is measured in kilowatt-hours, using a consumption meter. On that clock, from right to left, there is the hand of the unit, the ten, the hundred and the thousand. If a pointer is between two numbers, the last number passed by the pointer is considered. Suppose that the measurements indicated in the following diagrams were made in a city where the price per kilowatt hour was R $ 0.20.

To know the consumption, the first thing is to know what was the reading until the previous month and how much is the reading until the current month. The question says that from right to left there is unity, ten, hundred and thousands. And when a pointer is between two numbers, it considers the last number passed by the pointer. The catch is time to read the clock, the clocks are inverted.

The thousand one turns counterclockwise, the hundred clockwise, the ten counterclockwise and the unit clockwise. It is possible to see that clocks turn the other way around because the arrangement of the numbers is different, the zero on top, in each watch the 1 is on a different side.

Do you understand the prank? So you have to pay attention in the direction of the hand to avoid making a mistake, and then there’s a simple mallet, draw an arrow indicating the rotation of the clock so you don’t get confused.

To read the meter from last month, imagine the pointer going from zero to the direction of the arrow. In the thousands watch, the hand went from 2 to between 2 and 3, so it is considered 2, which was the last number passed by the hand.

In the hundred, the hand went through 5, following the rule you should consider 5. In the ten, the hand went through 6, then considers 6. In the unit the hand went through 3, so considers 3, so consumption in the last month was 2563 kWh.

We will perform the same process to read the current month’s meter, always pay close attention to the clock and hand. The thousand clock is 2, in the hundred it is 7, in the ten it is 8 and in the unit it is 3, so the accumulated consumption in the current month was 2783 kWh.

Now, to find out how much was spent in the month, you need to subtract how much was spent up to the current month from what had been spent up to the previous month. Consumption since the end of the previous month was 220 kWh.

Returning to the question, the price of kWh is R $ 0.20. If 220 kWh was spent in the month and each kWh costs 20 cents just multiply what was spent by the kWh value, obtaining 44 reais, so the correct answer is the letter E.