A resistor is a passive two-terminal electrical component that implements electrical resistance as a circuit element. In electronic circuits, resistors are used to reduce current flow, adjust signal levels, to divide voltages, bias active elements, and terminate transmission lines, among other uses.
Ohms Law and Power
- To find the Voltage, ( V ) [ V = I x R ] V (volts) = I (amps) x R (Ω)
- To find the Current, ( I ) [ I = V ÷ R ] I (amps) = V (volts) ÷ R (Ω)
- To find the Resistance, ( R ) [ R = V ÷ I ] R (Ω) = V (volts) ÷ I (amps)
- To find the Power (P) [ P = V x I ] P (watts) = V (volts) x I (amps)
By the current, the ammeter categorises into two types.
A voltmeter is an instrument used for measuring electric potential difference between two points in an electric circuit. It is connected in parallel. It usually has a high resistance so that it takes a negligible current from the circuit.
Ammeters are typically represented by a circle with a letter A inside (Figure 1). Figure 1. Symbol for ammeter. Voltmeters are typically represented by a circle with a letter V inside (Figure 2).
Most ammeter scales indicate the current being measured in increasing values from left to right. If you connect the meter without observing proper polarity, the pointer may be deflected backwards (from right to left). This action often damages the meter movement.
The principle of ammeter is that the resistance and inductive reactance must be very low. Ammeter has a very low impedance as the voltage drop across the ammeter should be low. The ammeter cannot be connected in parallel because of the above-mentioned reason.
Voltmeter is used to measure potential difference.It is always connected in parallel across the points where the potential difference is to measured so one end of the voltmeter is connected to the point A of a resistance AB and the other end to the point B,and also it has a high resistance so that it takes a negligible
A voltmeter is connected in parallel with a device to measure its voltage, while an ammeter is connected in series with a device to measure its current. At the heart of most analog meters is a galvanometer, an instrument that measures current flow using the movement, or deflection, of a needle.
IF VOLTMETER OR VOLTAGE IS CONNECTED IN SERIES THEN DUE TO HIGH RESISTANCE NO CURRENT WILL FLOW THROUGH CIRCUIT SO NO VOLTAGE DROP OCCUR.
Given emf E = 9 V , and that both resistances are equal, R = 1 kΩ , calculate the voltmeter reading if voltmeter's internal resistance is Rv = 10 kΩ . So far, I have calculated E * R2 / (R1 + R2) which gives me a result of 4.5V .
Hook up each wire to a post on the back of the ammeter (it doesn't matter which goes where) and see if you get a reading. If you get any reading at all, electricity will flow and your gauge is good! The number you get, in case you are curious, is the resistance in the gauge, and of course a lower number is best.
Note: Always connect the red (+) terminal on the ammeter to the positive terminal on the power supply.
Why is it a very bad idea to connect an ammeter directly across a voltage source, like this? Due to the ammeter's very low resistance, it will “draw” a lot of current from the voltage source. In effect, the ammeter will form a short circuit with the voltage source, potentially damaging the meter and/or the source.
Voltmeter and ammeter scales are read in the same manner. However, voltmeters measure volts, and ammeters measure amperes. The maximum value indicated by a meter is called the full-scale value. In other words, the maximum voltage or current that a meter can read is its full-scale value.
Just like voltmeters, ammeters tend to influence the amount of current in the circuits they're connected to. However, unlike the ideal voltmeter, the ideal ammeter has zero internal resistance, so as to drop as little voltage as possible as current flows through it.
Inclined Coil Iron Vane Meter
Ohmmeter, instrument for measuring electrical resistance, which is expressed in ohms. In the simplest ohmmeters, the resistance to be measured may be connected to the instrument in parallel or in series. Ratio meters measure the ratio of the voltage across the resistance to the current flowing through it.
Measuring current and voltage
- Current is measured in amperes. Amperes is often abbreviated to amps or A. The current flowing through a component in a circuit is measured using an ammeter.
- Voltage is measured in volts, often abbreviated to V.
- The voltmeter must be connected in parallel with the component.
Chapter 1 - Resistor fundamentalsThe resistor is a passive electrical component to create resistance in the flow of electric current. In almost all electrical networks and electronic circuits they can be found. The resistance is measured in ohms.
