Home Improvement Skills & Specialties Electrical

Amps vs. Volts: The Dangers of Electrical Shock

Learn the difference between amps and volts to stay safe during projects.

A person using a voltmeters to measure amperage.

 The Spruce / Margot Cavin

There are many dangers associated with electricity, namely regarding amperage and voltage. An accidental shock can cause severe burns, damage to internal organs, and even death. Most people think of electricity in terms of voltage, or they might note wattage (e.g., a 60-watt light bulb). However, when considering amperage vs. voltage, amperage is what you need to be concerned with when it comes to electrical shock.

Below, we've explained the key differences between amperage and voltage to help you better understand how to stay safe when working around electrical circuits.

Amperage vs. Voltage

The Spruce / Tara Anand

Voltage vs. Amperage

Voltage and amperage do not mean the same thing, though they both are measures of electrical current or flow of electrons. Voltage is a measure of the pressure that allows electrons to flow. Amperage is a measure of the volume of electrons.

Voltage

Think of voltage as the potential electricity that could run through an electrical system. Though the number may increase (12 volts, 120 volts, 240 volts), this is just the potential electricity from the source, not necessarily the amount of electricity traveling through the system.

An electrical supply of 1,000 volts is no more deadly than 100 volts, as the danger is determined by the current. Tiny changes in a current's amperage can mean the difference between life and death when a person receives an electrical shock. 

Amperage

Think of amperage as the amount of electricity that's traveling through the electrical system. For instance, the current of a 10-amp fuse on a 120-volt power supply isn't allowing the same volume of electricity to flow as a 15-amp fuse on the same 120-volt power supply.

Controlling an electrical circuit's current is crucial to making it compatible with whatever you intend to power. For example, if you plug a 15-amp hairdryer into an outlet supplied by only a 10-amp breaker, the hairdryer will not function properly and will likely trip the breaker.

However, moving to a plug tied to a 15-amp breaker will allow you to use the hairdryer. Both plugs are 120 volts, but the additional five amps allow an ample volume of electricity to meet the demands of the hairdryer's electrical load.

Tip

Fuses and breakers protect electrical systems and devices from electrical overload and other faults by limiting the current that can flow through them. If more than the allowed current attempts to flow through the fuse or breaker, the fuse "blows" or the breaker "trips," which breaks the path of electricity completely.

To better understand the relationship between voltage and amperage and how it affects the risk of electrical shock, imagine spraying someone with a water hose with a spray nozzle. For this analogy, consider the following:

  • Voltage = Water Spigot's Initial Pressure
  • Resistance = Hose With a Spray Nozzle
  • Amperage = Resulting Water Flow

Pulling the spray nozzle's trigger further would decrease the resistance, thus increasing the current. The initial water pressure (constant voltage) never changes.

However, the increase in the volume of water (increased amperage) due to the opened spray nozzle (decreased resistance) is what determines how soaked you get when sprayed. Thus, with amps vs. volts, the danger is in the amps.

Effects of Amperage on Electrical Shock

Different amounts of amperage affect the human body in different ways. The following list explains some of the most common effects of electrical shock at various amperage levels, according to the U.S. Occupational Safety and Health Administration (OSHA).

To understand the amounts involved, a milliampere (mA) is one-thousandth of an ampere (or amp). A standard household circuit that supplies your outlets and switches carries 15 or 20 amps (15,000 or 20,000 mA). 

  • 1 to 5 mA: Little electrical shock is felt; upsetting but not painful
  • 6 to 30 mA: Painful shock; loss of muscle control
  • 50 to 150 mA: Extreme pain; possible severe muscle reactions; possible respiratory arrest; possible death
  • 1,000 mA to 4,300 mA: Heart ceases pumping; nerve damage; death likely
  • 10,000 mA (10 amps): Cardiac arrest; severe burns; death likely

This gives you an idea of just how much danger there is in the home wiring system we take for granted, where wires carry 15,000 or 20,000 mA.

Warning

When working on or near home electrical components, always turn off the power at the breaker, then test the circuit using an electrical tester to confirm there's no power.

Staying Safe

The best way to prevent electrical shock is to follow standard safety procedures for all electrical work. Here are some of the most important basic safety rules:

  • Shut off the power: Always turn off the power to a circuit or device that you will be working on. The most reliable way to shut off the power is to switch off the breaker for the circuit in the home's service panel (breaker box).
  • Test for power: After turning off a circuit's breaker, check the wiring or devices you will be working on with a non-contact voltage tester, pre-tested on a known live circuit, to confirm the power is off. This is the only way to be sure you turned off the correct circuit.
  • Use insulated ladders: Never use an aluminum ladder for electrical work. Always use an insulated fiberglass ladder to keep you safe.
  • Stay dry: Avoid wet areas when working around electricity. If you are outdoors in damp or wet conditions, wear rubber boots and gloves to reduce the chance of getting shocked. Plug power tools and appliances into a GFCI (ground-fault circuit interrupter) outlet or GFCI extension cord. Dry your hands before grabbing any cord.
  • Post warnings: If you are working on the service panel or a circuit protected by a breaker within the panel, place a warning label on the face of the panel to warn others not to turn on any circuits. Before turning the power back on, make sure no one else is in contact with the circuit.

Understanding Watts and Ohms

Other electrical terms like watts and ohms can make matters more confusing when trying to understand the principles of electricity. That is, until you get a grasp of what these terms mean and how they relate to volts and amperage.

Watts

You've likely seen wattage ratings on light bulbs and wondered what this means, beyond the light being potentially brighter. Watts is the rate of power flow. When considering a 60-watt bulb, that number tells you how much power flow it takes to run that bulb.

You can use the watt value along with the voltage value to solve for the amp requirements with this equation:

  • Watts / Volts = Amps

This means that a 5,000-watt electric dryer plugged into a 240-volt outlet would require just over 20 amps of current, as 5,000 / 240 = 20.83.

Ohms

Another electrical term you might be familiar with is "ohms." Ohms, represented by the symbol Ω, measure resistance in electrical flow.

From the wiring to the appliance or device you're powering, nearly every component in the electrical system causes some resistance, or a slowing of the electrical current as it flows through the circuit.

While some resistance happens naturally as a result of the various electrical components, it's often intentionally introduced to control or limit the current with the help of resistors.

To solve for resistance, use this formula:

  • Ω = V / A or ohms = volts / amps

For instance, a 120-volt circuit with a current of 15 amps has a resistance of 8 ohms.

FAQ
  • How many amps are in a volt?

    One volt is the amount of pressure it takes to force one amp of electrical current against one ohm of resistance, meaning the resistance determines the current from a given voltage.


    So, if you decrease the resistance, you increase the amps. If you increase the resistance, you reduce the amps. A multimeter allows you to safely measure all of these electrical values and more.

  • How many amps are in 12/20/120/240 volt?

    To determine the amperage of a given voltage, you must divide the voltage by the resistance.


    For example, a 120-volt power supply with a resistance of 8 ohms draws 15 amps and a 240-volt power supply with a resistance of 4 ohms draws 60 amps. As you decrease resistance, you directly increase current.

  • How do you calculate watts from amps and volts?

    You can easily solve for wattage by multiplying amps and volts. For example, a 120-volt power supply with a current of 10 amps is 1,200 watts. Likewise, a 240-volt power supply with a current of 60 amps is 14,400 watts.

The Spruce uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Electrical Injuries. StatPearls.

  2. Basic Electrical Safety. United States Occupational Safety and Health Administration.