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Related Concept Videos

Magnetic Field Of A Current Loop01:16

Magnetic Field Of A Current Loop

Consider a circular loop with a radius a, that carries a current I. The magnetic field due to the current at an arbitrary point P along the axis of the loop can be calculated using the Biot-Savart law.
Magnetic Field Due to Two Straight Wires01:18

Magnetic Field Due to Two Straight Wires

Consider two parallel straight wires carrying a current of 10 A and 20 A in the same direction and separated by a distance of 20 cm. Calculate the magnetic field at a point "P2", midway between the wires. Also, evaluate the magnetic field when the direction of the current is reversed in the second wire.
Magnetic Field Due To A Thin Straight Wire01:27

Magnetic Field Due To A Thin Straight Wire

Consider an infinitely long straight wire carrying a current I. The magnetic field at point P at a distance a from the origin can be calculated using the Biot-Savart law.
Torque On A Current Loop In A Magnetic Field01:13

Torque On A Current Loop In A Magnetic Field

The most common application of magnetic force on current-carrying wires is in electric motors. These consist of loops of wire, which are placed between the magnets with a magnetic field. When current flows through the loops, the magnetic field applies torque, which causes the shaft to rotate, thus converting electrical energy to mechanical energy.
Consider a rectangular current-carrying loop containing N turns of wire, placed in a uniform magnetic field. The net force on a current-carrying loop...
Inductance: Solid Cylindrical Conductor01:24

Inductance: Solid Cylindrical Conductor

To calculate the inductance of a solid cylindrical conductor, consider a 1-meter section of a non-magnetic, current-carrying conductor with radius r. Disregarding end effects and assuming uniform current density, Ampere's law helps determine the magnetic field inside the conductor. This law states that the magnetic field intensity H is concentric and constant within the conductor.
Given the uniform current distribution, the magnetic field Hx and flux density Bx inside the conductor are...
Force On A Current Loop In A Magnetic Field01:17

Force On A Current Loop In A Magnetic Field

Magnetic forces on wires carrying current are most frequently applied in motors. A DC motor is a device that converts electrical energy into mechanical work. In motors, wire loops are enclosed in a magnetic field. When current flows through the loops, the magnetic field applies torque, which causes the shaft to rotate. The direction of the current is reversed once the loop's surface area is lined up with the magnetic field, causing a constant torque on the loop. During the process, commutators...

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Related Experiment Video

Updated: Jun 25, 2026

MRM Microcoil Performance Calibration and Usage Demonstrated on Medicago truncatula Roots at 22 T
10:22

MRM Microcoil Performance Calibration and Usage Demonstrated on Medicago truncatula Roots at 22 T

Published on: January 16, 2021

Noise figure limits for circular loop MR coils.

Ananda Kumar1, William A Edelstein, Paul A Bottomley

  • 1Department of Radiology, Division of MR Research, Johns Hopkins University, Baltimore, Maryland 21205, USA.

Magnetic Resonance in Medicine
|March 3, 2009
PubMed
Summary
This summary is machine-generated.

Coil noise figure (NF) quantifies detector noise in MRI. Reducing loop size increases coil noise, impacting signal-to-noise ratio (SNR). This study quantifies coil losses to optimize MRI detector design.

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Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples
07:01

Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples

Published on: June 9, 2016

Related Experiment Videos

Last Updated: Jun 25, 2026

MRM Microcoil Performance Calibration and Usage Demonstrated on Medicago truncatula Roots at 22 T
10:22

MRM Microcoil Performance Calibration and Usage Demonstrated on Medicago truncatula Roots at 22 T

Published on: January 16, 2021

Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples
07:01

Frequency Mixing Magnetic Detection Scanner for Imaging Magnetic Particles in Planar Samples

Published on: June 9, 2016

Area of Science:

  • Magnetic Resonance Imaging (MRI)
  • Electromagnetics
  • Medical Physics

Background:

  • Circular loops are standard MRI detectors, with arrays enhancing signal-to-noise ratio (SNR) and spatial resolution.
  • Decreasing loop size elevates coil noise relative to sample noise, potentially limiting SNR.

Purpose of the Study:

  • To quantify relative noise contributions from the sample and coil using a coil noise figure (NF(coil)).
  • To determine NF(coil) based on coil quality factors (Q) and analyze losses across various frequencies and coil designs.

Main Methods:

  • Measured and computed coil losses (conductors, capacitors, eddy currents) from 40 to 400 MHz using analytical and numerical electromagnetic analysis.
  • Measured unloaded-to-loaded coil quality factors (Q) for wire and tape loops.
  • Determined NF(coil) as a function of coil radius, frequency, and tuning capacitors.

Main Results:

  • Computed and experimental Q and NF(coil) values showed agreement within approximately 10%.
  • NF(coil) for 3 cm wire coils decreased significantly with increasing magnetic field strength (e.g., 3 dB at 1T to 0.1 dB at 9.4T).
  • Tape coils in arrays exhibited substantial eddy current losses compared to wire coils.

Conclusions:

  • Characterizing and predicting coil losses are crucial for designing SNR-optimized loop and phased-array MRI detectors.
  • Understanding NF(coil) is essential for improving MRI performance, especially at higher field strengths.